small cleanups aggregated
A few cleanups that I've found myself making repeatedly in WIP branches, figured it was worth pushing them to avoid cluttering diffs down the road.

- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19328?src=pr&el=h1) Report
> Merging [#19328](https://codecov.io/gh/pandas-dev/pandas/pull/19328?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/1245f0673074316b53d1d1ee10abd6077058b133?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/19328/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/19328?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #19328      +/-   ##
==========================================
- Coverage   91.53%   91.52%   -0.01%     
==========================================
  Files         150      150              
  Lines       48739    48725      -14     
==========================================
- Hits        44612    44595      -17     
- Misses       4127     4130       +3
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.89% <100%> (-0.01%)` | :arrow_down: |
| #single | `41.73% <80%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/19328?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexes/range.py](https://codecov.io/gh/pandas-dev/pandas/pull/19328/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9yYW5nZS5weQ==) | `95.7% <ø> (ø)` | :arrow_up: |
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/19328/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `96.46% <100%> (ø)` | :arrow_up: |
| [pandas/core/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/19328/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvb3BzLnB5) | `94.95% <100%> (+1.84%)` | :arrow_up: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/19328/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `65.22% <0%> (-1.74%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/19328?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/19328?src=pr&el=footer). Last update [1245f06...3a56faa](https://codecov.io/gh/pandas-dev/pandas/pull/19328?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks!