DOC: update the pd.Index.asof docstring
Checklist for the pandas documentation sprint (ignore this if you are doing
an unrelated PR):

- [x] PR title is "DOC: update the <your-function-or-method> docstring"
- [x] The validation script passes: `scripts/validate_docstrings.py <your-function-or-method>`
- [x] The PEP8 style check passes: `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] The html version looks good: `python doc/make.py --single <your-function-or-method>`
- [x] It has been proofread on language by another sprint participant

Please include the output of the validation script below between the "```" ticks:

```
################################################################################
######################## Docstring (pandas.Index.asof)  ########################
################################################################################

Return the latest index label up to and including the passed label.

For sorted indexes, return the index label that is the latest among
the labels that are not later than the passed index label.

Parameters
----------
label : object
    The label up to which the method returns the latest index label.

Returns
-------
object : The index label that is the latest as of the passed label,
    or NaN if there is no such label.

See also
--------
Index.get_loc : `asof` is a thin wrapper around `get_loc`
    with method='pad'.

Examples
--------
13 is the latest index label up to 14.

>>> pd.Index([13, 18, 20]).asof(14)
13

If the label is in the index, the method returns the passed label.

>>> pd.Index([13, 18, 20]).asof(18)
18

If all of the labels in the index are later than the passed label,
NaN is returned.

>>> pd.Index([13, 18, 20]).asof(1)
nan

If the index is not sorted, an error is raised.

>>> pd.Index([13, 20, 18]).asof(18)
Traceback (most recent call last):
ValueError: index must be monotonic increasing or decreasing

################################################################################
################################## Validation ##################################
################################################################################

Docstring for "pandas.Index.asof" correct. :)

```

If the validation script still gives errors, but you think there is a good reason
to deviate in this case (and there are certainly such cases), please state this
explicitly.


# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/20344?src=pr&el=h1) Report
> Merging [#20344](https://codecov.io/gh/pandas-dev/pandas/pull/20344?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/cdfce2b0ad99f7faad57cc5247cf33aab5725bed?src=pr&el=desc) will **decrease** coverage by `0.04%`.
> The diff coverage is `90.47%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/20344/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/20344?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #20344      +/-   ##
==========================================
- Coverage   91.82%   91.77%   -0.05%     
==========================================
  Files         152      153       +1     
  Lines       49248    49270      +22     
==========================================
- Hits        45222    45220       -2     
- Misses       4026     4050      +24
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.17% <90.47%> (-0.05%)` | :arrow_down: |
| #single | `41.89% <90.47%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/20344?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/20344/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `96.63% <90.47%> (-0.06%)` | :arrow_down: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/20344/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `63.2% <0%> (-1.88%)` | :arrow_down: |
| [pandas/io/clipboard/clipboards.py](https://codecov.io/gh/pandas-dev/pandas/pull/20344/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2NsaXBib2FyZC9jbGlwYm9hcmRzLnB5) | `30.58% <0%> (-1.6%)` | :arrow_down: |
| [pandas/core/nanops.py](https://codecov.io/gh/pandas-dev/pandas/pull/20344/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvbmFub3BzLnB5) | `95.13% <0%> (-1.57%)` | :arrow_down: |
| [pandas/core/config\_init.py](https://codecov.io/gh/pandas-dev/pandas/pull/20344/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29uZmlnX2luaXQucHk=) | `99.24% <0%> (-0.76%)` | :arrow_down: |
| [pandas/core/arrays/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/20344/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2NhdGVnb3JpY2FsLnB5) | `95.7% <0%> (-0.49%)` | :arrow_down: |
| [pandas/core/resample.py](https://codecov.io/gh/pandas-dev/pandas/pull/20344/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzYW1wbGUucHk=) | `96.06% <0%> (-0.37%)` | :arrow_down: |
| [pandas/util/\_decorators.py](https://codecov.io/gh/pandas-dev/pandas/pull/20344/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvX2RlY29yYXRvcnMucHk=) | `82.25% <0%> (-0.15%)` | :arrow_down: |
| [pandas/plotting/\_core.py](https://codecov.io/gh/pandas-dev/pandas/pull/20344/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb3JlLnB5) | `82.39% <0%> (-0.12%)` | :arrow_down: |
| [pandas/io/pytables.py](https://codecov.io/gh/pandas-dev/pandas/pull/20344/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3B5dGFibGVzLnB5) | `92.41% <0%> (-0.05%)` | :arrow_down: |
| ... and [34 more](https://codecov.io/gh/pandas-dev/pandas/pull/20344/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/20344?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/20344?src=pr&el=footer). Last update [cdfce2b...9bc532a](https://codecov.io/gh/pandas-dev/pandas/pull/20344?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Hello @datapythonista I've updated the documentation based on your suggestions. Do you think it's okay now to be merged? Not exactly sure how to proceed now. Should I ping a core developer and ask for merge? @DataOmbudsman  no need for that. Project maintainers and core developers are in most cases volunteers, that use their spare time to work on the projects. They will take a look at this when they have the time. In many cases that will be in few hours or couple of days. In other cases it can take weeks. You just need to wait. If you check it, you'll see that there are 165 pull requests like yours open. Be patient, and work in something else if you've got the time. :) @datapythonista All right, thanks for the clarification. :)  Thanks @DataOmbudsman! Sorry for the delay on our end. Great docstring!