DOC: Fixing some more warnings
- [X] closes #26788, xref #24173
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Fixing some more warnings in the doc build, and small improvements to the interpolation doc.

CC: @jorisvandenbossche 
BTW, the issue for the problem with the IPython directive is here: https://github.com/ipython/ipython/issues/11362 @jorisvandenbossche any idea why I'm getting a lot of those locally:
```
.. autoproperty:: categories
/home/mgarcia/src/pandas/doc/source/reference/api/pandas.Categorical.codes.rst:6: WARNING: Unknown directive type "autoproperty".
```

I think it started after downgrading sphinx back to 1.8.5 > any idea why I'm getting a lot of those locally:

Not sure, I also don't see those on the PR pinning to 1.8.5 > any idea why I'm getting a lot of those locally:

did you do a full clean build? It might be that the api rst pages generated by sphinx 2 are not compatible with 1.8.5 ? # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26810?src=pr&el=h1) Report
> Merging [#26810](https://codecov.io/gh/pandas-dev/pandas/pull/26810?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/8ff488ac1078c49a0db23562db41dae9e41b053b?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26810/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26810?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26810      +/-   ##
==========================================
- Coverage   91.76%   91.75%   -0.01%     
==========================================
  Files         178      178              
  Lines       50751    50751              
==========================================
- Hits        46574    46569       -5     
- Misses       4177     4182       +5
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.35% <ø> (ø)` | :arrow_up: |
| #single | `41.2% <ø> (-0.11%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26810?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/26810/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `78.94% <0%> (-10.53%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/26810/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.88% <0%> (-0.12%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/26810/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `90.84% <0%> (-0.11%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26810?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/26810?src=pr&el=footer). Last update [8ff488a...3d43234](https://codecov.io/gh/pandas-dev/pandas/pull/26810?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/26810?src=pr&el=h1) Report
> Merging [#26810](https://codecov.io/gh/pandas-dev/pandas/pull/26810?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/e8132a2901075b96b0d6e74639d5c341bec115fe?src=pr&el=desc) will **increase** coverage by `1.4%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26810/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26810?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##           master   #26810     +/-   ##
=========================================
+ Coverage   90.45%   91.86%   +1.4%     
=========================================
  Files         179      179             
  Lines       50706    50706             
=========================================
+ Hits        45866    46579    +713     
+ Misses       4840     4127    -713
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.45% <ø> (ø)` | :arrow_up: |
| #single | `41.09% <ø> (?)` | |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26810?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/26810/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `90.94% <0%> (+0.1%)` | :arrow_up: |
| [pandas/core/arrays/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/26810/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL2NhdGVnb3JpY2FsLnB5) | `95.92% <0%> (+0.12%)` | :arrow_up: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/26810/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `96.37% <0%> (+0.16%)` | :arrow_up: |
| [pandas/io/formats/printing.py](https://codecov.io/gh/pandas-dev/pandas/pull/26810/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvcHJpbnRpbmcucHk=) | `85.56% <0%> (+1.06%)` | :arrow_up: |
| [pandas/io/clipboard/clipboards.py](https://codecov.io/gh/pandas-dev/pandas/pull/26810/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2NsaXBib2FyZC9jbGlwYm9hcmRzLnB5) | `34.78% <0%> (+2.89%)` | :arrow_up: |
| [pandas/core/computation/expr.py](https://codecov.io/gh/pandas-dev/pandas/pull/26810/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vZXhwci5weQ==) | `97.8% <0%> (+3.02%)` | :arrow_up: |
| [pandas/core/computation/common.py](https://codecov.io/gh/pandas-dev/pandas/pull/26810/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vY29tbW9uLnB5) | `89.47% <0%> (+5.26%)` | :arrow_up: |
| [pandas/io/pytables.py](https://codecov.io/gh/pandas-dev/pandas/pull/26810/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3B5dGFibGVzLnB5) | `90.29% <0%> (+26.47%)` | :arrow_up: |
| [pandas/core/computation/pytables.py](https://codecov.io/gh/pandas-dev/pandas/pull/26810/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vcHl0YWJsZXMucHk=) | `90.24% <0%> (+27.74%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26810?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/26810?src=pr&el=footer). Last update [e8132a2...bd5afaa](https://codecov.io/gh/pandas-dev/pandas/pull/26810?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @jorisvandenbossche this should be ready, after this there aren't many warnings left. Some tricky ones but we're not that far.

I see many of this type:
```
2019-06-13T09:16:31.8908721Z /home/vsts/work/1/s/doc/source/reference/api/pandas.arrays.DatetimeArray.map.rst: WARNING: document isn't included in any toctree
2019-06-13T09:16:31.8910069Z /home/vsts/work/1/s/doc/source/reference/api/pandas.arrays.DatetimeArray.ndim.rst: WARNING: document isn't included in any toctree
2019-06-13T09:16:31.8911939Z /home/vsts/work/1/s/doc/source/reference/api/pandas.arrays.IntegerArray.dtype.rst: WARNING: document isn't included in any toctree
2019-06-13T09:16:31.8913217Z /home/vsts/work/1/s/doc/source/reference/api/pandas.arrays.IntervalArray.argsort.rst: WARNING: document isn't included in any toctree
2019-06-13T09:16:31.8914672Z /home/vsts/work/1/s/doc/source/reference/api/pandas.arrays.IntervalArray.astype.rst: WARNING: document isn't included in any toctree
```

Checking the first one, I see in http://dev.pandas.io/reference/api/pandas.arrays.DatetimeArray.html that `map` is indeed not included in the toctree. But in the docstring I see that the attributes and methods are actually not explicit, but added automatically: https://github.com/pandas-dev/pandas/blob/master/pandas/core/arrays/datetimes.py#L214

Any idea what's the problem/how to fix those? Thanks! @datapythonista DatetimeArray.map's doesn't have a docstring, and it may not inherit one. Can you see if adding a simple docstring fixes that warning?

edit: IntegerArray.dtype also doesn't have a docstring.  For IntervalArray.{argsort,astype}, I think they will need to be added to the list of methods in the class docstring. > For IntervalArray.{argsort,astype}, I think they will need to be added to the list of methods in the class docstring.

Or not? (because I don't think we want them in the API reference for each array?) Hmm, right I was thinking about it backwards (thinking we had a ref, but no target). I wonder why it's being generated then. Looking at the code, I think we should take the "class_without_autosummary" template approach for all our internal EAs as well (which we currently don't do apparently, except for Categorical). Trying that out now. See https://github.com/pandas-dev/pandas/pull/26834 Looks good to me. Can you open an issue about the changes here that should be reverted once the cause is fixed? (the added okwarning/okexcepts) Opened an issue for those okwarning/okexcepts: https://github.com/pandas-dev/pandas/issues/26843