docstring and whitespace cleanup
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/21719?src=pr&el=h1) Report
> Merging [#21719](https://codecov.io/gh/pandas-dev/pandas/pull/21719?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/79bc3357fc30faf1f98b8815fcb02ea9bec154fb?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/21719/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/21719?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #21719   +/-   ##
=======================================
  Coverage   91.92%   91.92%           
=======================================
  Files         158      158           
  Lines       49698    49698           
=======================================
  Hits        45684    45684           
  Misses       4014     4014
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.29% <ø> (ø)` | :arrow_up: |
| #single | `42% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/21719?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/21719?src=pr&el=footer). Last update [79bc335...1fe67a2](https://codecov.io/gh/pandas-dev/pandas/pull/21719?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks @jbrockmendel 