CLN: ASV inference benchmark
- Flake8 and removed star imports

- Used `params` and `setup_cache` where possible

```
asv dev -b ^inference
· Discovering benchmarks
· Running 13 total benchmarks (1 commits * 1 environments * 13 benchmarks)
[  0.00%] ·· Building for existing-py_home_matt_anaconda_envs_pandas_dev_bin_python
[  0.00%] ·· Benchmarking existing-py_home_matt_anaconda_envs_pandas_dev_bin_python
[  0.00%] ··· Setting up /home/matt/Projects/pandas-mroeschke/asv_bench/benchmarks/inference.py:105
[  7.69%] ··· Running inference.MaybeConvertNumeric.time_convert                                                                    2.55s
[ 15.38%] ··· Running inference.NumericInferOps.time_add                                                                               ok
[ 15.38%] ···· 
               ========= ========
                 dtype           
               --------- --------
                 int64    7.27ms 
                 int32    4.09ms 
                 uint32   2.33ms 
                float32   3.98ms 
                float64   7.20ms 
               ========= ========

[ 23.08%] ··· Running inference.NumericInferOps.time_divide                                                                            ok
[ 23.08%] ···· 
               ========= ========
                 dtype           
               --------- --------
                 int64    9.22ms 
                 int32    7.77ms 
                 uint32   6.34ms 
                float32   4.00ms 
                float64   7.25ms 
               ========= ========

[ 30.77%] ··· Running inference.NumericInferOps.time_modulo                                                                            ok
[ 30.77%] ···· 
               ========= ========
                 dtype           
               --------- --------
                 int64    17.3ms 
                 int32    9.96ms 
                 uint32   10.3ms 
                float32   8.27ms 
                float64   8.37ms 
               ========= ========

[ 38.46%] ··· Running inference.NumericInferOps.time_multiply                                                                          ok
[ 38.46%] ···· 
               ========= ========
                 dtype           
               --------- --------
                 int64    7.18ms 
                 int32    4.12ms 
                 uint32   2.42ms 
                float32   4.08ms 
                float64   7.15ms 
               ========= ========

[ 46.15%] ··· Running inference.NumericInferOps.time_subtract                                                                          ok
[ 46.15%] ···· 
               ========= ========
                 dtype           
               --------- --------
                 int64    7.23ms 
                 int32    3.96ms 
                 uint32   2.36ms 
                float32   3.96ms 
                float64   7.12ms 
               ========= ========

[ 53.85%] ··· Running inference.ToNumeric.time_from_float                                                                              ok
[ 53.85%] ···· 
               ======== =======
                errors         
               -------- -------
                ignore   157μs 
                coerce   158μs 
               ======== =======

[ 61.54%] ··· Running inference.ToNumeric.time_from_numeric_str                                                                        ok
[ 61.54%] ···· 
               ======== ========
                errors          
               -------- --------
                ignore   8.08ms 
                coerce   8.05ms 
               ======== ========

[ 69.23%] ··· Running inference.ToNumeric.time_from_str                                                                                ok
[ 69.23%] ···· 
               ======== ========
                errors          
               -------- --------
                ignore   365μs  
                coerce   24.7ms 
               ======== ========

[ 76.92%] ··· Running inference.ToNumericDowncast.time_downcast                                                                        ok
[ 76.92%] ···· 
               ============== ======== ========= ======== ========== ========
               --                                 downcast                   
               -------------- -----------------------------------------------
                   dtype        None    integer   signed   unsigned   float  
               ============== ======== ========= ======== ========== ========
                string-float   264ms     270ms    272ms     267ms     268ms  
                 string-int    597ms     621ms    640ms     612ms     605ms  
                string-nint    613ms     622ms    631ms     597ms     610ms  
                 datetime64    5.17ms    72.0ms   72.3ms    74.3ms    8.87ms 
                  int-list     65.0ms    92.7ms   92.5ms    94.5ms    66.8ms 
                   int32       26.2μs    27.2ms   26.9ms    27.9ms    1.35ms 
               ============== ======== ========= ======== ========== ========

[ 76.92%] ··· Setting up /home/matt/Projects/pandas-mroeschke/asv_bench/benchmarks/inference.py:40
[ 84.62%] ··· Running inference.DateInferOps.time_add_timedeltas                                                                   29.1ms
[ 92.31%] ··· Running inference.DateInferOps.time_subtract_datetimes                                                               23.6ms
[100.00%] ··· Running inference.DateInferOps.time_timedelta_plus_datetime                                                           157ms
```

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18759?src=pr&el=h1) Report
> Merging [#18759](https://codecov.io/gh/pandas-dev/pandas/pull/18759?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/9705a480615201ce1e89e5385f48fde155726e8b?src=pr&el=desc) will **decrease** coverage by `0.02%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18759/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/18759?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18759      +/-   ##
==========================================
- Coverage   91.61%   91.59%   -0.03%     
==========================================
  Files         153      153              
  Lines       51363    51363              
==========================================
- Hits        47058    47047      -11     
- Misses       4305     4316      +11
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.46% <ø> (-0.01%)` | :arrow_down: |
| #single | `40.75% <ø> (-0.12%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18759?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18759/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/18759/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `82.32% <0%> (-0.2%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18759/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.81% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18759?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18759?src=pr&el=footer). Last update [9705a48...d9fc6f4](https://codecov.io/gh/pandas-dev/pandas/pull/18759?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18759?src=pr&el=h1) Report
> Merging [#18759](https://codecov.io/gh/pandas-dev/pandas/pull/18759?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/9705a480615201ce1e89e5385f48fde155726e8b?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18759/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/18759?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18759      +/-   ##
==========================================
+ Coverage   91.61%   91.61%   +<.01%     
==========================================
  Files         153      154       +1     
  Lines       51363    51430      +67     
==========================================
+ Hits        47058    47120      +62     
- Misses       4305     4310       +5
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.48% <ø> (+0.02%)` | :arrow_up: |
| #single | `40.83% <ø> (-0.04%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18759?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18759/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18759/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.68% <0%> (-0.23%)` | :arrow_down: |
| [pandas/core/internals.py](https://codecov.io/gh/pandas-dev/pandas/pull/18759/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzLnB5) | `94.42% <0%> (-0.02%)` | :arrow_down: |
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/18759/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `95.9% <0%> (ø)` | :arrow_up: |
| [pandas/core/apply.py](https://codecov.io/gh/pandas-dev/pandas/pull/18759/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXBwbHkucHk=) | `99.42% <0%> (ø)` | |
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/18759/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `96.44% <0%> (ø)` | :arrow_up: |
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/18759/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `94.82% <0%> (ø)` | :arrow_up: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/18759/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.71% <0%> (+0.01%)` | :arrow_up: |
| [pandas/core/sparse/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18759/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc3BhcnNlL2ZyYW1lLnB5) | `94.8% <0%> (+0.02%)` | :arrow_up: |
| [pandas/core/indexes/interval.py](https://codecov.io/gh/pandas-dev/pandas/pull/18759/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9pbnRlcnZhbC5weQ==) | `93.83% <0%> (+0.03%)` | :arrow_up: |
| ... and [3 more](https://codecov.io/gh/pandas-dev/pandas/pull/18759/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18759?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18759?src=pr&el=footer). Last update [9705a48...8c2f3f6](https://codecov.io/gh/pandas-dev/pandas/pull/18759?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Created a new `numeric_dtypes` variable in `pandas_vb_common.py` of numpy numeric types, adjusted import and added back `int(N / 2)` for compat. 

```
asv dev -b ^inference
· Discovering benchmarks
· Running 13 total benchmarks (1 commits * 1 environments * 13 benchmarks)
[  0.00%] ·· Building for existing-py_home_matt_anaconda_envs_pandas_dev_bin_python
[  0.00%] ·· Benchmarking existing-py_home_matt_anaconda_envs_pandas_dev_bin_python
[  0.00%] ··· Setting up /home/matt/Projects/pandas-mroeschke/asv_bench/benchmarks/inference.py:43
[  7.69%] ··· Running inference.DateInferOps.time_add_timedeltas                                                        35.0ms
[ 15.38%] ··· Running inference.DateInferOps.time_subtract_datetimes                                                    23.7ms
[ 23.08%] ··· Running inference.DateInferOps.time_timedelta_plus_datetime                                                156ms
[ 23.08%] ··· Setting up /home/matt/Projects/pandas-mroeschke/asv_bench/benchmarks/inference.py:108
[ 30.77%] ··· Running inference.MaybeConvertNumeric.time_convert                                                         2.58s
[ 38.46%] ··· Running inference.NumericInferOps.time_add                                                                    ok
[ 38.46%] ···· 
               ======================== ========
                        dtype                   
               ------------------------ --------
                 <type 'numpy.int64'>    7.21ms 
                 <type 'numpy.int32'>    3.98ms 
                <type 'numpy.uint32'>    2.31ms 
                <type 'numpy.uint64'>    4.16ms 
                <type 'numpy.float32'>   3.89ms 
                <type 'numpy.float64'>   7.12ms 
                 <type 'numpy.int16'>    1.84ms 
                 <type 'numpy.int8'>     1.36ms 
                <type 'numpy.uint16'>    1.97ms 
                 <type 'numpy.uint8'>    1.54ms 
               ======================== ========

[ 46.15%] ··· Running inference.NumericInferOps.time_divide                                                                 ok
[ 46.15%] ···· 
               ======================== ========
                        dtype                   
               ------------------------ --------
                 <type 'numpy.int64'>    9.17ms 
                 <type 'numpy.int32'>    7.76ms 
                <type 'numpy.uint32'>    6.36ms 
                <type 'numpy.uint64'>    6.52ms 
                <type 'numpy.float32'>   4.02ms 
                <type 'numpy.float64'>   7.21ms 
                 <type 'numpy.int16'>    6.97ms 
                 <type 'numpy.int8'>     6.83ms 
                <type 'numpy.uint16'>    7.02ms 
                 <type 'numpy.uint8'>    6.98ms 
               ======================== ========

[ 53.85%] ··· Running inference.NumericInferOps.time_modulo                                                                 ok
[ 53.85%] ···· 
               ======================== ========
                        dtype                   
               ------------------------ --------
                 <type 'numpy.int64'>    17.6ms 
                 <type 'numpy.int32'>    10.1ms 
                <type 'numpy.uint32'>    9.58ms 
                <type 'numpy.uint64'>    13.9ms 
                <type 'numpy.float32'>   8.22ms 
                <type 'numpy.float64'>   8.31ms 
                 <type 'numpy.int16'>    8.61ms 
                 <type 'numpy.int8'>     15.1ms 
                <type 'numpy.uint16'>    8.19ms 
                 <type 'numpy.uint8'>    14.3ms 
               ======================== ========

[ 61.54%] ··· Running inference.NumericInferOps.time_multiply                                                               ok
[ 61.54%] ···· 
               ======================== ========
                        dtype                   
               ------------------------ --------
                 <type 'numpy.int64'>    7.25ms 
                 <type 'numpy.int32'>    4.12ms 
                <type 'numpy.uint32'>    2.39ms 
                <type 'numpy.uint64'>    4.11ms 
                <type 'numpy.float32'>   4.06ms 
                <type 'numpy.float64'>   7.08ms 
                 <type 'numpy.int16'>    1.51ms 
                 <type 'numpy.int8'>     1.09ms 
                <type 'numpy.uint16'>    1.52ms 
                 <type 'numpy.uint8'>    1.16ms 
               ======================== ========

[ 69.23%] ··· Running inference.NumericInferOps.time_subtract                                                               ok
[ 69.23%] ···· 
               ======================== ========
                        dtype                   
               ------------------------ --------
                 <type 'numpy.int64'>    7.20ms 
                 <type 'numpy.int32'>    4.05ms 
                <type 'numpy.uint32'>    2.46ms 
                <type 'numpy.uint64'>    4.06ms 
                <type 'numpy.float32'>   3.93ms 
                <type 'numpy.float64'>   7.31ms 
                 <type 'numpy.int16'>    1.62ms 
                 <type 'numpy.int8'>     1.12ms 
                <type 'numpy.uint16'>    1.84ms 
                 <type 'numpy.uint8'>    1.23ms 
               ======================== ========

[ 76.92%] ··· Running inference.ToNumeric.time_from_float                                                                   ok
[ 76.92%] ···· 
               ======== =======
                errors         
               -------- -------
                ignore   166μs 
                coerce   156μs 
               ======== =======

[ 84.62%] ··· Running inference.ToNumeric.time_from_numeric_str                                                             ok
[ 84.62%] ···· 
               ======== ========
                errors          
               -------- --------
                ignore   8.47ms 
                coerce   8.93ms 
               ======== ========

[ 92.31%] ··· Running inference.ToNumeric.time_from_str                                                                     ok
[ 92.31%] ···· 
               ======== ========
                errors          
               -------- --------
                ignore   357μs  
                coerce   25.6ms 
               ======== ========

[100.00%] ··· Running inference.ToNumericDowncast.time_downcast                                                             ok
[100.00%] ···· 
               ============== ======== ========= ======== ========== ========
               --                                 downcast                   
               -------------- -----------------------------------------------
                   dtype        None    integer   signed   unsigned   float  
               ============== ======== ========= ======== ========== ========
                string-float   270ms     268ms    264ms     271ms     283ms  
                 string-int    605ms     630ms    640ms     634ms     620ms  
                string-nint    622ms     643ms    686ms     650ms     611ms  
                 datetime64    5.38ms    76.7ms   72.3ms    85.6ms    9.01ms 
                  int-list     64.6ms    94.3ms   93.2ms    95.3ms    66.8ms 
                   int32       26.4μs    27.1ms   27.2ms    28.0ms    1.42ms 
               ============== ======== ========= ======== ========== ========
``` @jorisvandenbossche changed the `lib` import to import from `pandas_vb_common.py` thanks!