ENH: maybe_convert_objects seen NaT speed-up
- [X] closes #27299
- [X] tests added / passed
- [X] passes `black pandas`
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [X] whatsnew entry

Will add. Should I add 'what's new' entry as well?

Also - in which file should I add asv - algorithms.py?  > Will add. Should I add 'what's new' entry as well?

yes that would be great; 0.25.0 performance section. ```
$ asv continuous master maybe_convert_objects_ENH -f 1.1 -b algorithms.MaybeConvertObjects
· Creating environments
· Discovering benchmarks
·· Uninstalling from conda-py3.6-Cython-matplotlib-numexpr-numpy-openpyxl-pytables-pytest-scipy-sqlalchemy-xlrd-xlsxwriter-xlwt
·· Building 56002cdd <maybe_convert_objects_ENH> for conda-py3.6-Cython-matplotlib-numexpr-numpy-openpyxl-pytables-pytest-scipy-sqlalchemy-xlrd-xlsxwriter-xlwt.......................................................
·· Installing 56002cdd <maybe_convert_objects_ENH> into conda-py3.6-Cython-matplotlib-numexpr-numpy-openpyxl-pytables-pytest-scipy-sqlalchemy-xlrd-xlsxwriter-xlwt..
· Running 2 total benchmarks (2 commits * 1 environments * 1 benchmarks)
[  0.00%] · For pandas commit c64c9cb4 <master> (round 1/2):
[  0.00%] ·· Building for conda-py3.6-Cython-matplotlib-numexpr-numpy-openpyxl-pytables-pytest-scipy-sqlalchemy-xlrd-xlsxwriter-xlwt..........................................................
[  0.00%] ·· Benchmarking conda-py3.6-Cython-matplotlib-numexpr-numpy-openpyxl-pytables-pytest-scipy-sqlalchemy-xlrd-xlsxwriter-xlwt
[ 25.00%] ··· Running (algorithms.MaybeConvertObjects.time_maybe_convert_objects--).
[ 25.00%] · For pandas commit 56002cdd <maybe_convert_objects_ENH> (round 1/2):
[ 25.00%] ·· Building for conda-py3.6-Cython-matplotlib-numexpr-numpy-openpyxl-pytables-pytest-scipy-sqlalchemy-xlrd-xlsxwriter-xlwt...
[ 25.00%] ·· Benchmarking conda-py3.6-Cython-matplotlib-numexpr-numpy-openpyxl-pytables-pytest-scipy-sqlalchemy-xlrd-xlsxwriter-xlwt
[ 50.00%] ··· Running (algorithms.MaybeConvertObjects.time_maybe_convert_objects--).
[ 50.00%] · For pandas commit 56002cdd <maybe_convert_objects_ENH> (round 2/2):
[ 50.00%] ·· Benchmarking conda-py3.6-Cython-matplotlib-numexpr-numpy-openpyxl-pytables-pytest-scipy-sqlalchemy-xlrd-xlsxwriter-xlwt
[ 75.00%] ··· algorithms.MaybeConvertObjects.time_maybe_convert_objects                                                                                                                                   17.1±0.3μs
[ 75.00%] · For pandas commit c64c9cb4 <master> (round 2/2):
[ 75.00%] ·· Building for conda-py3.6-Cython-matplotlib-numexpr-numpy-openpyxl-pytables-pytest-scipy-sqlalchemy-xlrd-xlsxwriter-xlwt...
[ 75.00%] ·· Benchmarking conda-py3.6-Cython-matplotlib-numexpr-numpy-openpyxl-pytables-pytest-scipy-sqlalchemy-xlrd-xlsxwriter-xlwt
[100.00%] ··· algorithms.MaybeConvertObjects.time_maybe_convert_objects                                                                                                                                   17.5±0.8ms
       before           after         ratio
     [c64c9cb4]       [56002cdd]
     <master>         <maybe_convert_objects_ENH>
-      17.5±0.8ms       17.1±0.3μs     0.00  algorithms.MaybeConvertObjects.time_maybe_convert_objects

SOME BENCHMARKS HAVE CHANGED SIGNIFICANTLY.
PERFORMANCE INCREASED.

``` I believe imports should be in this order:
```python
import pandas as pd
from pandas._libs import lib
from pandas.util import testing as tm
```
But  when I run `isort --recursive --check-only pandas` locally it only prints `Skipped 3 files` without errors. Or am I checked it wrong? Also maybe add `isort --recursive --check-only pandas` to the initial list of TODO's of PRs? Along with `black pandas` and `git diff upstream/master -u -- "*.py" | flake8 --diff`. Full asv 
```
asv continuous -f 1.1 master maybe_convert_objects_ENH
```
returns:
```
+      14.1±0.1ms       19.8±0.4ms     1.41  strings.Cat.time_cat(0, None, '-', 0.0)
+      2.92±0.1ms       4.06±0.3ms     1.39  algorithms.Quantile.time_quantile(0.5, 'midpoint', 'uint')
+        479±10μs         665±70μs     1.39  categoricals.Constructor.time_from_codes_all_int8
+     2.78±0.08ms       3.84±0.4ms     1.38  algorithms.Quantile.time_quantile(0.5, 'midpoint', 'int')
+      14.2±0.4ms       19.6±0.9ms     1.38  strings.Cat.time_cat(0, None, None, 0.0)
+      14.2±0.2ms       19.5±0.5ms     1.38  strings.Cat.time_cat(0, ',', None, 0.0)
+     4.62±0.07ms       6.30±0.4ms     1.37  algorithms.Quantile.time_quantile(0.5, 'midpoint', 'float')
+      14.3±0.3ms       19.4±0.7ms     1.35  strings.Cat.time_cat(0, ',', '-', 0.0)
+     2.47±0.08ms       3.31±0.3ms     1.34  algorithms.Quantile.time_quantile(1, 'nearest', 'float')
+      66.1±0.5ms        83.5±10ms     1.26  strings.Methods.time_rfind
+        729±60μs        913±200μs     1.25  ctors.SeriesConstructors.time_series_constructor(<function list_of_str at 0x7f6cf3692bf8>, False, 'int')
+     2.87±0.04ms       3.55±0.2ms     1.24  algorithms.Quantile.time_quantile(0.5, 'higher', 'uint')
+        894±30μs      1.10±0.02ms     1.23  indexing.NonNumericSeriesIndexing.time_getitem_pos_slice('string', 'unique_monotonic_inc')
+     9.73±0.09ms       11.7±0.9ms     1.21  series_methods.ValueCounts.time_value_counts('object')
+      7.08±0.1ms       8.46±0.2ms     1.20  timeseries.ResampleSeries.time_resample('datetime', '5min', 'mean')
+        814±80μs        964±200μs     1.18  ctors.SeriesConstructors.time_series_constructor(<function list_of_str at 0x7f6cf3692bf8>, True, 'int')
+      25.4±0.3ms         29.6±2ms     1.16  categoricals.Indexing.time_reindex
+      3.00±0.1ms       3.46±0.1ms     1.15  rolling.Quantile.time_quantile('Series', 1000, 'int', 1, 'nearest')
+      4.01±0.2ms       4.51±0.7ms     1.12  ctors.SeriesConstructors.time_series_constructor(<function gen_of_tuples at 0x7f6cf36a9400>, False, 'int')
+         813±9μs         913±10μs     1.12  series_methods.IsInForObjects.time_isin_nans
+      2.60±0.1ms       2.92±0.2ms     1.12  ctors.SeriesConstructors.time_series_constructor(<class 'list'>, False, 'int')
+     2.66±0.07ms      2.97±0.06ms     1.12  ctors.SeriesConstructors.time_series_constructor(<class 'list'>, True, 'int')
+     4.86±0.04ms      5.42±0.09ms     1.12  timeseries.ToDatetimeISO8601.time_iso8601_format_no_sep
+         142±3μs          158±9μs     1.11  ctors.SeriesConstructors.time_series_constructor(<function no_change at 0x7f6cf3692b70>, True, 'int')
+        866±80μs         955±70μs     1.10  ctors.SeriesConstructors.time_series_constructor(<function list_of_str at 0x7f6cf3692bf8>, True, 'float')
-         262±3μs          238±9μs     0.91  groupby.GroupByMethods.time_dtype_as_group('float', 'all', 'direct')
-        575±10μs          521±6μs     0.91  groupby.GroupByMethods.time_dtype_as_group('object', 'head', 'direct')
-        91.5±5ms         82.8±1ms     0.90  io.sql.WriteSQLDtypes.time_to_sql_dataframe_column('sqlalchemy', 'datetime')
-        641±10μs          580±3μs     0.90  groupby.GroupByMethods.time_dtype_as_group('float', 'tail', 'transformation')
-     1.68±0.04μs      1.52±0.05μs     0.90  period.PeriodProperties.time_property('min', 'hour')
-         336±5μs          303±4μs     0.90  offset.OffsetDatetimeIndexArithmetic.time_add_offset(<YearBegin: month=1>)
-         155±6ms        140±0.3ms     0.90  io.csv.ReadCSVDInferDatetimeFormat.time_read_csv(False, 'custom')
-      50.4±0.7ms         45.3±1ms     0.90  groupby.Nth.time_frame_nth_any('object')
-        467±20μs          420±9μs     0.90  groupby.GroupByMethods.time_dtype_as_group('int', 'min', 'transformation')
-      1.65±0.1μs      1.49±0.02μs     0.90  period.PeriodProperties.time_property('min', 'minute')
-        353±30μs          317±8μs     0.90  indexing_engines.NumericEngineIndexing.time_get_loc((<class 'pandas._libs.index.UInt32Engine'>, <class 'numpy.uint32'>), 'non_monotonic')
-         216±2μs          193±6μs     0.90  groupby.GroupByMethods.time_dtype_as_group('object', 'size', 'transformation')
-     1.60±0.01ms      1.43±0.05ms     0.89  groupby.GroupByMethods.time_dtype_as_group('int', 'value_counts', 'direct')
-         491±6ns          439±5ns     0.89  timestamp.TimestampProperties.time_days_in_month(tzutc(), 'B')
-        172±20ms          153±2ms     0.89  io.json.ToJSON.time_delta_int_tstamp('split')
-        497±10ns          442±6ns     0.89  timestamp.TimestampProperties.time_days_in_month(<UTC>, 'B')
-        83.6±7μs         74.4±2μs     0.89  inference.ToNumeric.time_from_float('ignore')
-      7.96±0.1ms       7.08±0.1ms     0.89  rolling.VariableWindowMethods.time_rolling('DataFrame', '50s', 'int', 'kurt')
-      6.15±0.5μs      5.46±0.06μs     0.89  io.hdf.HDFStoreDataFrame.time_store_repr
-         178±7ms          158±2ms     0.89  io.sql.SQL.time_to_sql_dataframe('sqlalchemy')
-        432±10ms          384±3ms     0.89  io.json.ReadJSONLines.time_read_json_lines_concat('int')
-     1.71±0.02μs      1.52±0.01μs     0.89  period.PeriodProperties.time_property('M', 'year')
-         494±4ns          437±6ns     0.89  timestamp.TimestampProperties.time_days_in_month(None, None)
-        477±30μs          422±3μs     0.89  indexing_engines.NumericEngineIndexing.time_get_loc((<class 'pandas._libs.index.Int64Engine'>, <class 'numpy.int64'>), 'non_monotonic')
-      6.67±0.2ms       5.89±0.2ms     0.88  indexing.Take.time_take('int')
-         376±4ms          332±4ms     0.88  groupby.GroupByMethods.time_dtype_as_group('int', 'skew', 'transformation')
-      3.45±0.1ms      3.04±0.07ms     0.88  indexing.NumericSeriesIndexing.time_getitem_list_like(<class 'pandas.core.indexes.numeric.Int64Index'>, 'nonunique_monotonic_inc')
-      1.39±0.04s       1.23±0.01s     0.88  join_merge.MergeAsof.time_multiby('nearest')
-        821±10μs         724±20μs     0.88  groupby.GroupByMethods.time_dtype_as_group('float', 'sum', 'transformation')
-         462±4μs         407±20μs     0.88  groupby.GroupByMethods.time_dtype_as_group('float', 'last', 'transformation')
-      5.03±0.1ms      4.42±0.08ms     0.88  io.csv.ReadUint64Integers.time_read_uint64
-         280±4μs          246±5μs     0.88  groupby.GroupByMethods.time_dtype_as_group('float', 'count', 'direct')
-      3.33±0.2ms      2.92±0.08ms     0.88  io.csv.ReadCSVCachedParseDates.time_read_csv_cached(True)
-         375±9ms         328±10ms     0.88  groupby.GroupByMethods.time_dtype_as_group('int', 'skew', 'direct')
-      1.69±0.1μs      1.48±0.03μs     0.88  period.PeriodProperties.time_property('M', 'dayofweek')
-         149±7μs          130±1μs     0.87  series_methods.NanOps.time_func('skew', 1000, 'int8')
-        639±30μs         558±10μs     0.87  groupby.GroupByMethods.time_dtype_as_group('int', 'nunique', 'transformation')
-      2.22±0.2ms      1.93±0.01ms     0.87  reshape.SparseIndex.time_unstack
-      2.82±0.2ms      2.46±0.03ms     0.87  reshape.SimpleReshape.time_unstack
-        937±20μs         818±10μs     0.87  indexing.NumericSeriesIndexing.time_loc_slice(<class 'pandas.core.indexes.numeric.Int64Index'>, 'nonunique_monotonic_inc')
-         484±7μs          422±6μs     0.87  groupby.GroupByMethods.time_dtype_as_group('float', 'max', 'direct')
-         284±7μs          248±7μs     0.87  groupby.GroupByMethods.time_dtype_as_group('int', 'shift', 'transformation')
-      4.20±0.1ms      3.66±0.02ms     0.87  join_merge.Merge.time_merge_dataframe_integer_key(True)
-     2.52±0.08ms      2.19±0.04ms     0.87  io.csv.ReadCSVFloatPrecision.time_read_csv(',', '.', None)
-      1.70±0.1μs      1.47±0.02μs     0.87  period.PeriodProperties.time_property('min', 'month')
-         266±2μs          231±5μs     0.87  groupby.GroupByMethods.time_dtype_as_group('float', 'any', 'direct')
-         160±9ms          139±2ms     0.87  io.json.ToJSON.time_floats_with_dt_index_lines('split')
-        27.6±2ms       23.9±0.6ms     0.87  io.sql.WriteSQLDtypes.time_to_sql_dataframe_column('sqlite', 'float')
-      12.8±0.9ms       11.1±0.2ms     0.87  reindex.LibFastZip.time_lib_fast_zip
-         194±2μs          168±4μs     0.87  indexing.NumericSeriesIndexing.time_ix_slice(<class 'pandas.core.indexes.numeric.Float64Index'>, 'unique_monotonic_inc')
-        283±20μs          245±5μs     0.86  groupby.GroupByMethods.time_dtype_as_group('float', 'shift', 'direct')
-     1.72±0.08μs      1.49±0.01μs     0.86  period.PeriodProperties.time_property('M', 'dayofyear')
-        971±70μs         839±10μs     0.86  indexing.NumericSeriesIndexing.time_loc_slice(<class 'pandas.core.indexes.numeric.Float64Index'>, 'nonunique_monotonic_inc')
-         224±1μs          193±2μs     0.86  groupby.GroupByMethods.time_dtype_as_group('float', 'size', 'transformation')
-       654±200μs         563±20μs     0.86  groupby.GroupByMethods.time_dtype_as_group('float', 'tail', 'direct')
-        875±20μs          753±6μs     0.86  indexing.NonNumericSeriesIndexing.time_getitem_pos_slice('string', 'non_monotonic')
-     1.33±0.05ms      1.14±0.01ms     0.86  groupby.GroupByMethods.time_dtype_as_field('datetime', 'rank', 'direct')
-        47.5±6ms       40.8±0.9ms     0.86  plotting.TimeseriesPlotting.time_plot_regular_compat
-         217±5μs          186±1μs     0.86  groupby.GroupByMethods.time_dtype_as_field('datetime', 'size', 'direct')
-        32.7±1ms       28.0±0.9ms     0.86  io.sql.WriteSQLDtypes.time_to_sql_dataframe_column('sqlite', 'float_with_nan')
-      4.00±0.3ms      3.42±0.03ms     0.86  rolling.VariableWindowMethods.time_rolling('DataFrame', '1d', 'int', 'mean')
-       1.33±0.1s       1.14±0.01s     0.86  join_merge.MergeAsof.time_multiby('forward')
-        654±40μs         558±20μs     0.85  groupby.GroupByMethods.time_dtype_as_group('float', 'quantile', 'direct')
-     1.47±0.09ms      1.25±0.06ms     0.85  groupby.GroupByMethods.time_dtype_as_group('object', 'value_counts', 'direct')
-     1.50±0.04ms      1.28±0.02ms     0.85  groupby.GroupByMethods.time_dtype_as_group('datetime', 'rank', 'transformation')
-     3.21±0.04ms      2.73±0.09ms     0.85  indexing.NumericSeriesIndexing.time_loc_list_like(<class 'pandas.core.indexes.numeric.UInt64Index'>, 'nonunique_monotonic_inc')
-        499±20μs         424±10μs     0.85  groupby.GroupByMethods.time_dtype_as_group('float', 'min', 'transformation')
-     1.32±0.07ms      1.12±0.01ms     0.85  indexing.DataFrameNumericIndexing.time_bool_indexer
-        371±10μs          314±6μs     0.85  indexing.NumericSeriesIndexing.time_ix_scalar(<class 'pandas.core.indexes.numeric.Int64Index'>, 'nonunique_monotonic_inc')
-        20.5±5μs       17.4±0.2μs     0.85  index_object.Indexing.time_slice_step('Float')
-        70.2±7μs         59.4±2μs     0.85  series_methods.NanOps.time_func('argmax', 1000, 'int32')
-        503±50μs          425±6μs     0.84  stat_ops.SeriesOps.time_op('mean', 'float', True)
-        413±20ms         348±10ms     0.84  io.stata.StataMissing.time_write_stata('tq')
-        205±10ms          173±3ms     0.84  io.json.ToJSON.time_float_int_str_lines('split')
-        27.8±1ms       23.4±0.2ms     0.84  io.sql.WriteSQLDtypes.time_to_sql_dataframe_column('sqlite', 'string')
-        138±10ms          116±1ms     0.84  reshape.Cut.time_qcut_int(1000)
-        70.7±7μs         59.5±3μs     0.84  series_methods.NanOps.time_func('argmax', 1000, 'int8')
-        801±30μs          674±8μs     0.84  io.parsers.ConcatDateCols.time_check_concat('AAAA', 1)
-      2.37±0.2ms      2.00±0.03ms     0.84  groupby.GroupByMethods.time_dtype_as_group('int', 'pct_change', 'direct')
-        633±40μs          530±3μs     0.84  groupby.GroupByMethods.time_dtype_as_group('datetime', 'nunique', 'direct')
-     1.85±0.06μs      1.55±0.02μs     0.84  period.PeriodProperties.time_property('M', 'qyear')
-        599±10μs         501±20μs     0.84  groupby.GroupByMethods.time_dtype_as_group('object', 'tail', 'direct')
-      1.76±0.2μs      1.47±0.01μs     0.84  period.PeriodProperties.time_property('min', 'dayofyear')
-        42.1±5ms       35.1±0.9ms     0.83  io.sql.SQL.time_read_sql_query('sqlalchemy')
-      3.55±0.3ms      2.95±0.08ms     0.83  io.parsers.ConcatDateCols.time_check_concat(1234567890, 2)
-      9.72±0.9ms       8.06±0.5ms     0.83  series_methods.NanOps.time_func('std', 1000000, 'int32')
-        60.8±5ms       50.2±0.8ms     0.82  io.sql.ReadSQLTable.time_read_sql_table_all
-     1.56±0.06ms      1.28±0.02ms     0.82  groupby.GroupByMethods.time_dtype_as_group('float', 'rank', 'direct')
-        601±10μs         493±10μs     0.82  indexing.NumericSeriesIndexing.time_ix_scalar(<class 'pandas.core.indexes.numeric.Float64Index'>, 'nonunique_monotonic_inc')
-     5.00±0.03ms      4.09±0.05ms     0.82  indexing.NonNumericSeriesIndexing.time_getitem_list_like('string', 'non_monotonic')
-        83.2±5ms         68.1±2ms     0.82  io.hdf.HDFStoreDataFrame.time_read_store_table_mixed
-        63.9±6ms         52.3±1ms     0.82  io.sql.WriteSQLDtypes.time_to_sql_dataframe_column('sqlalchemy', 'string')
-         123±6ms          101±2ms     0.82  multiindex_object.Duplicated.time_duplicated
-      1.22±0.06s         992±10ms     0.81  join_merge.I8Merge.time_i8merge('left')
-        231±20μs          188±3μs     0.81  groupby.GroupByMethods.time_dtype_as_group('int', 'size', 'transformation')
-        134±10μs          109±3μs     0.81  series_methods.NanOps.time_func('argmax', 1000, 'float64')
-      8.49±0.1ms       6.88±0.2ms     0.81  io.sas.SAS.time_read_msgpack('xport')
-        289±10μs         233±10μs     0.81  groupby.GroupByMethods.time_dtype_as_group('float', 'shift', 'transformation')
-        225±20μs          181±4μs     0.81  indexing.NumericSeriesIndexing.time_loc_scalar(<class 'pandas.core.indexes.numeric.UInt64Index'>, 'unique_monotonic_inc')
-     1.10±0.06ms         890±10μs     0.81  indexing.NumericSeriesIndexing.time_ix_slice(<class 'pandas.core.indexes.numeric.Int64Index'>, 'nonunique_monotonic_inc')
-        351±20μs          281±6μs     0.80  inference.NumericInferOps.time_add(<class 'numpy.uint8'>)
-        37.2±5ms       29.8±0.5ms     0.80  io.sql.SQL.time_read_sql_query('sqlite')
-        23.4±1ms       18.7±0.8ms     0.80  multiindex_object.Integer.time_get_indexer
-        156±10ms          124±2ms     0.79  io.sas.SAS.time_read_msgpack('sas7bdat')
-      3.63±0.1ms       2.87±0.1ms     0.79  indexing.NumericSeriesIndexing.time_loc_list_like(<class 'pandas.core.indexes.numeric.Float64Index'>, 'nonunique_monotonic_inc')
-         250±7ms          198±2ms     0.79  inference.ToNumericDowncast.time_downcast('string-int', None)
-     1.19±0.03ms         944±20μs     0.79  indexing.NumericSeriesIndexing.time_ix_slice(<class 'pandas.core.indexes.numeric.Float64Index'>, 'nonunique_monotonic_inc')
-       92.7±20μs       72.9±0.7μs     0.79  inference.ToNumeric.time_from_float('coerce')
-        24.3±3ms       19.1±0.4ms     0.79  groupby.Nth.time_frame_nth('float32')
-      11.7±0.7ms       9.07±0.3ms     0.78  reindex.DropDuplicates.time_frame_drop_dups_int(True)
-        74.9±6ms         58.3±5ms     0.78  io.parsers.DoesStringLookLikeDatetime.time_check_datetimes('0.0')
-        354±30μs          273±4μs     0.77  join_merge.Concat.time_concat_empty_left(0)
-      2.01±0.2ms      1.54±0.03ms     0.77  reindex.LevelAlign.time_align_level
-         108±4ms         80.6±8ms     0.75  io.parsers.DoesStringLookLikeDatetime.time_check_datetimes('10000')
-        83.2±2ms         58.8±1ms     0.71  io.sql.WriteSQLDtypes.time_to_sql_dataframe_column('sqlalchemy', 'bool')
-      23.0±0.4ms       16.2±0.5ms     0.70  indexing.NumericSeriesIndexing.time_ix_scalar(<class 'pandas.core.indexes.numeric.UInt64Index'>, 'nonunique_monotonic_inc')
-        48.7±1ms         33.6±2ms     0.69  io.msgpack.MSGPack.time_write_msgpack
-        442±30μs          297±6μs     0.67  indexing.NumericSeriesIndexing.time_ix_slice(<class 'pandas.core.indexes.numeric.UInt64Index'>, 'unique_monotonic_inc')
-      1.98±0.3ms      1.32±0.02ms     0.67  io.parsers.ConcatDateCols.time_check_concat(1234567890, 1)
-     1.97±0.09ms      1.31±0.04ms     0.66  groupby.GroupByMethods.time_dtype_as_group('float', 'sem', 'direct')
-      1.11±0.3ms         703±10μs     0.63  groupby.GroupByMethods.time_dtype_as_group('int', 'prod', 'transformation')
-        16.2±1ms       10.2±0.2ms     0.63  reindex.DropDuplicates.time_frame_drop_dups_na(True)
-        36.1±3ms       22.5±0.6ms     0.62  io.msgpack.MSGPack.time_read_msgpack
-        3.25±2μs      1.62±0.01μs     0.50  period.PeriodProperties.time_property('min', 'week')
-        3.02±1μs      1.50±0.05μs     0.50  period.PeriodProperties.time_property('min', 'qyear')
-      16.2±0.3ms         19.1±1μs     0.00  algorithms.MaybeConvertObjects.time_maybe_convert_objects

```
So there are (somehow) downsides of it (or I am using `asv` wrong, or interpret results of `asv` wrong) - need recheck it.

Btw full `asv` gets 3-4 hours without build for my laptop. So it is not fast here. Yea I think there is some noise in there - do some of the regressions even hit this code? ok so likely is this path is not hit in our asvs

so remove the whatsnew note and looks good  thanks @BeforeFlight followups welcome.