DOC: some doc fixes
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17913?src=pr&el=h1) Report
> :exclamation: No coverage uploaded for pull request base (`master@5687f9e`). [Click here to learn what that means](https://docs.codecov.io/docs/error-reference#section-missing-base-commit).
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17913/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/17913?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##             master   #17913   +/-   ##
=========================================
  Coverage          ?   91.22%           
=========================================
  Files             ?      163           
  Lines             ?    50107           
  Branches          ?        0           
=========================================
  Hits              ?    45710           
  Misses            ?     4397           
  Partials          ?        0
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.03% <ø> (?)` | |
| #single | `40.31% <ø> (?)` | |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17913?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/17913?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `92.53% <ø> (ø)` | |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17913?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.75% <ø> (ø)` | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17913?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/17913?src=pr&el=footer). Last update [5687f9e...9b480d7](https://codecov.io/gh/pandas-dev/pandas/pull/17913?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
