DOC: Mention both series and dataframe mirror methods
- [x] closes #21825

Now the automatically-generated doc features both `Series` and `Dataframe` in the _See also:_ section.

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/21840?src=pr&el=h1) Report
> Merging [#21840](https://codecov.io/gh/pandas-dev/pandas/pull/21840?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/3fa171fc86963e8a775f3b2322b16d5c0b19fbd2?src=pr&el=desc) will **increase** coverage by `0.26%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/21840/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/21840?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #21840      +/-   ##
==========================================
+ Coverage   91.92%   92.18%   +0.26%     
==========================================
  Files         160      169       +9     
  Lines       49916    50820     +904     
==========================================
+ Hits        45885    46850     +965     
+ Misses       4031     3970      -61
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.6% <100%> (+0.29%)` | :arrow_up: |
| #single | `42.38% <0%> (+0.26%)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/21840?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/21840/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `96.67% <100%> (+0.21%)` | :arrow_up: |
| [pandas/util/\_depr\_module.py](https://codecov.io/gh/pandas-dev/pandas/pull/21840/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvX2RlcHJfbW9kdWxlLnB5) | `65.11% <0%> (-13.96%)` | :arrow_down: |
| [pandas/util/\_tester.py](https://codecov.io/gh/pandas-dev/pandas/pull/21840/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvX3Rlc3Rlci5weQ==) | `23.8% <0%> (-5.61%)` | :arrow_down: |
| [pandas/io/clipboard/clipboards.py](https://codecov.io/gh/pandas-dev/pandas/pull/21840/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2NsaXBib2FyZC9jbGlwYm9hcmRzLnB5) | `28.23% <0%> (-2.36%)` | :arrow_down: |
| [pandas/core/indexes/period.py](https://codecov.io/gh/pandas-dev/pandas/pull/21840/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9wZXJpb2QucHk=) | `93.48% <0%> (-0.76%)` | :arrow_down: |
| [pandas/core/reshape/pivot.py](https://codecov.io/gh/pandas-dev/pandas/pull/21840/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9waXZvdC5weQ==) | `96.55% <0%> (-0.49%)` | :arrow_down: |
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/21840/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `93.74% <0%> (-0.46%)` | :arrow_down: |
| [pandas/plotting/\_tools.py](https://codecov.io/gh/pandas-dev/pandas/pull/21840/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL190b29scy5weQ==) | `72.62% <0%> (-0.31%)` | :arrow_down: |
| [pandas/core/reshape/reshape.py](https://codecov.io/gh/pandas-dev/pandas/pull/21840/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9yZXNoYXBlLnB5) | `99.54% <0%> (-0.25%)` | :arrow_down: |
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/21840/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `96.39% <0%> (-0.19%)` | :arrow_down: |
| ... and [98 more](https://codecov.io/gh/pandas-dev/pandas/pull/21840/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/21840?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/21840?src=pr&el=footer). Last update [3fa171f...cd15aa4](https://codecov.io/gh/pandas-dev/pandas/pull/21840?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @datapythonista if you have any comments. Hello @teoguso! Thanks for updating the PR.

 - There are no PEP8 issues in the file [`pandas/core/generic.py`](https://github.com/teoguso/pandas/blob/cd15aa4837ad97c4a61cd8441a3ad6fbc29f615b/pandas/core/generic.py) !

 closing as stale. if you'd like to continue, pls ping. @jreback this is not stale, it's ready to be merged @teoguso can you please merge master and fix the conflicts? @teoguso do you have time to fix the conflicts, so we can merge? @datapythonista 