DOC: Removal of return variable names [WIP]
@datapythonista 

This is part of the sprint (3rd February). It removes the return variable name from the docstrings.
Looks generally good. Can you post the output of the validation script for the affected entries? # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25123?src=pr&el=h1) Report
> Merging [#25123](https://codecov.io/gh/pandas-dev/pandas/pull/25123?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/a814ea480e416f14550d9dd9e16c19d69619663f?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25123/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25123?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #25123   +/-   ##
=======================================
  Coverage   92.37%   92.37%           
=======================================
  Files         166      166           
  Lines       52415    52415           
=======================================
  Hits        48418    48418           
  Misses       3997     3997
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.79% <100%> (ø)` | :arrow_up: |
| #single | `42.87% <100%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25123?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/25123/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `96.63% <100%> (ø)` | :arrow_up: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/25123/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.82% <0%> (ø)` | :arrow_up: |
| [pandas/core/arrays/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/25123/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2NhdGVnb3JpY2FsLnB5) | `95.97% <0%> (ø)` | :arrow_up: |
| [pandas/core/window.py](https://codecov.io/gh/pandas-dev/pandas/pull/25123/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvd2luZG93LnB5) | `96.4% <0%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25123?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/25123?src=pr&el=footer). Last update [a814ea4...381650e](https://codecov.io/gh/pandas-dev/pandas/pull/25123?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/25123?src=pr&el=h1) Report
> Merging [#25123](https://codecov.io/gh/pandas-dev/pandas/pull/25123?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/a814ea480e416f14550d9dd9e16c19d69619663f?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25123/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25123?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #25123   +/-   ##
=======================================
  Coverage   92.37%   92.37%           
=======================================
  Files         166      166           
  Lines       52415    52415           
=======================================
  Hits        48418    48418           
  Misses       3997     3997
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.79% <100%> (ø)` | :arrow_up: |
| #single | `42.87% <100%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25123?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/25123/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `96.63% <100%> (ø)` | :arrow_up: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/25123/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.82% <0%> (ø)` | :arrow_up: |
| [pandas/core/arrays/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/25123/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2NhdGVnb3JpY2FsLnB5) | `95.97% <0%> (ø)` | :arrow_up: |
| [pandas/core/window.py](https://codecov.io/gh/pandas-dev/pandas/pull/25123/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvd2luZG93LnB5) | `96.4% <0%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25123?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/25123?src=pr&el=footer). Last update [a814ea4...381650e](https://codecov.io/gh/pandas-dev/pandas/pull/25123?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @WillAyd - where can I find it? What is it called? @hannah-c `python scripts/validate_docstrings.py <name>` where `<name>` is like `pandas.Series.mad`  thanks @hannah-c  @hannah-c if you want to double check that everything looks good now that this is merged, in around an hour or later you can check the development documentation: https://pandas-docs.github.io/pandas-docs-travis/