Precursor for #25607
- [x] precursor for #25607
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
Nothing new

Can you summarize what's changing here, and the reason for it? @impact27 happy to take straight reorg that passes everywhere. pls merge master. and update to comments. I will take care of that over the next few days, probably this week-end.

> On 26 Mar 2019, at 00:21, Jeff Reback <notifications@github.com> wrote:
> 
> @impact27 <https://github.com/impact27> happy to take straight reorg that passes everywhere. pls merge master. and update to comments.
> 
> —
> You are receiving this because you were mentioned.
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> 

 Hello @impact27! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:



There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2019-04-27 16:04:12 UTC # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25688?src=pr&el=h1) Report
> Merging [#25688](https://codecov.io/gh/pandas-dev/pandas/pull/25688?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/26d991fc4e568432c3264151265c0a3ea9a6f133?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `85.24%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25688/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25688?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #25688      +/-   ##
==========================================
+ Coverage   91.28%   91.28%   +<.01%     
==========================================
  Files         173      173              
  Lines       52965    52974       +9     
==========================================
+ Hits        48348    48358      +10     
+ Misses       4617     4616       -1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.86% <85.24%> (ø)` | :arrow_up: |
| #single | `41.74% <39.34%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25688?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexing.py](https://codecov.io/gh/pandas-dev/pandas/pull/25688/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhpbmcucHk=) | `90.95% <85.24%> (+0.07%)` | :arrow_up: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/25688/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `89.08% <0%> (+0.09%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25688?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/25688?src=pr&el=footer). Last update [26d991f...05047f1](https://codecov.io/gh/pandas-dev/pandas/pull/25688?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/25688?src=pr&el=h1) Report
> Merging [#25688](https://codecov.io/gh/pandas-dev/pandas/pull/25688?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/64104ec343f0770afa88f02da47b34fbe62c8281?src=pr&el=desc) will **decrease** coverage by `50.08%`.
> The diff coverage is `49.31%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/25688/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/25688?src=pr&el=tree)

```diff
@@             Coverage Diff             @@
##           master   #25688       +/-   ##
===========================================
- Coverage   91.97%   41.89%   -50.09%     
===========================================
  Files         175      174        -1     
  Lines       52379    52555      +176     
===========================================
- Hits        48178    22018    -26160     
- Misses       4201    30537    +26336
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `?` | |
| #single | `41.89% <49.31%> (+1.04%)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/25688?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexing.py](https://codecov.io/gh/pandas-dev/pandas/pull/25688/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhpbmcucHk=) | `52.9% <49.31%> (-37.63%)` | :arrow_down: |
| [pandas/io/formats/latex.py](https://codecov.io/gh/pandas-dev/pandas/pull/25688/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvbGF0ZXgucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/sas/sas\_constants.py](https://codecov.io/gh/pandas-dev/pandas/pull/25688/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXNfY29uc3RhbnRzLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/core/groupby/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/25688/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9jYXRlZ29yaWNhbC5weQ==) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/tseries/plotting.py](https://codecov.io/gh/pandas-dev/pandas/pull/25688/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvcGxvdHRpbmcucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/tseries/converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/25688/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvY29udmVydGVyLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/formats/html.py](https://codecov.io/gh/pandas-dev/pandas/pull/25688/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvaHRtbC5weQ==) | `0% <0%> (-99.37%)` | :arrow_down: |
| [pandas/io/sas/sas7bdat.py](https://codecov.io/gh/pandas-dev/pandas/pull/25688/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXM3YmRhdC5weQ==) | `0% <0%> (-91.16%)` | :arrow_down: |
| [pandas/io/sas/sas\_xport.py](https://codecov.io/gh/pandas-dev/pandas/pull/25688/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXNfeHBvcnQucHk=) | `0% <0%> (-90.1%)` | :arrow_down: |
| [pandas/core/tools/numeric.py](https://codecov.io/gh/pandas-dev/pandas/pull/25688/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvdG9vbHMvbnVtZXJpYy5weQ==) | `10.44% <0%> (-89.56%)` | :arrow_down: |
| ... and [138 more](https://codecov.io/gh/pandas-dev/pandas/pull/25688/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/25688?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/25688?src=pr&el=footer). Last update [64104ec...6fcbcfd](https://codecov.io/gh/pandas-dev/pandas/pull/25688?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @impact27 do we need this PR or is it a duplicate of the other one you link to?  This one doesn’t do anything, it is just code reorganisation. The idea is to not do too many things in one PR.

> On 10 Apr 2019, at 06:35, William Ayd <notifications@github.com> wrote:
> 
> @impact27 do we need this PR or is it a duplicate of the other one you link to?
> 
> —
> You are receiving this because you were mentioned.
> Reply to this email directly, view it on GitHub, or mute the thread.
 @impact27 if you can merge master and get passing, pls ping pls merge master; ping when passing closing as stale; ping if you want to continue