TST: clean up series/frame api tests inheritance a bit
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=h1) Report
> Merging [#15949](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/f35209e2279154ed7060dd0e17d41da96f9c0186?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/15949/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&height=150&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #15949   +/-   ##
=======================================
  Coverage      91%      91%           
=======================================
  Files         145      145           
  Lines       49576    49576           
=======================================
  Hits        45118    45118           
  Misses       4458     4458
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.77% <100%> (ø)` | :arrow_up: |
| #single | `40.57% <0%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree#diff-cGFuZGFzL2luZGV4ZXMvYmFzZS5weQ==) | `96.09% <100%> (ø)` | :arrow_up: |
| [pandas/tseries/index.py](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvaW5kZXgucHk=) | `95.43% <100%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/15949?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/15949?src=pr&el=footer). Last update [f35209e...6a899d3](https://codecov.io/gh/pandas-dev/pandas/pull/15949?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/15949?src=pr&el=h1) Report
> Merging [#15949](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/f35209e2279154ed7060dd0e17d41da96f9c0186?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/15949/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #15949   +/-   ##
=======================================
  Coverage      91%      91%           
=======================================
  Files         145      145           
  Lines       49576    49576           
=======================================
  Hits        45118    45118           
  Misses       4458     4458
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.77% <100%> (ø)` | :arrow_up: |
| #single | `40.57% <0%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree#diff-cGFuZGFzL2luZGV4ZXMvYmFzZS5weQ==) | `96.09% <100%> (ø)` | :arrow_up: |
| [pandas/tseries/index.py](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvaW5kZXgucHk=) | `95.43% <100%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/15949?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/15949?src=pr&el=footer). Last update [f35209e...6a899d3](https://codecov.io/gh/pandas-dev/pandas/pull/15949?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/15949?src=pr&el=h1) Report
> Merging [#15949](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/9cb2c2db0dd763bb9e6586d3103a564875ed25d5?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/15949/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #15949      +/-   ##
==========================================
- Coverage      91%      91%   -0.01%     
==========================================
  Files         145      145              
  Lines       49581    49576       -5     
==========================================
- Hits        45123    45118       -5     
  Misses       4458     4458
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.77% <100%> (-0.01%)` | :arrow_down: |
| #single | `40.57% <0%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree#diff-cGFuZGFzL2luZGV4ZXMvYmFzZS5weQ==) | `96.09% <100%> (ø)` | :arrow_up: |
| [pandas/tseries/index.py](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvaW5kZXgucHk=) | `95.43% <100%> (ø)` | :arrow_up: |
| [pandas/core/algorithms.py](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYWxnb3JpdGhtcy5weQ==) | `94.53% <0%> (-0.05%)` | :arrow_down: |
| [pandas/core/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYmFzZS5weQ==) | `95.51% <0%> (ø)` | :arrow_up: |
| [pandas/core/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY2F0ZWdvcmljYWwucHk=) | `95.85% <0%> (ø)` | :arrow_up: |
| [pandas/indexes/api.py](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree#diff-cGFuZGFzL2luZGV4ZXMvYXBpLnB5) | `98.66% <0%> (ø)` | :arrow_up: |
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `94.89% <0%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/15949?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/15949?src=pr&el=footer). Last update [9cb2c2d...2f6a9c2](https://codecov.io/gh/pandas-dev/pandas/pull/15949?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).