Fix doc string of make_signature() function
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @srinivasreddy! Thanks for updating the PR.

 - There are no PEP8 issues in the file [`pandas/api/extensions/__init__.py`](https://github.com/srinivasreddy/pandas/blob/4c2f32899b8033863034627ca64a9df61cfcbf1b/pandas/api/extensions/__init__.py) !

 - There are no PEP8 issues in the file [`pandas/util/_decorators.py`](https://github.com/srinivasreddy/pandas/blob/4c2f32899b8033863034627ca64a9df61cfcbf1b/pandas/util/_decorators.py) !



##### Comment last updated on November 21, 2018 at 14:41 Hours UTC # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23768?src=pr&el=h1) Report
> :exclamation: No coverage uploaded for pull request base (`master@6e932f8`). [Click here to learn what that means](https://docs.codecov.io/docs/error-reference#section-missing-base-commit).
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23768/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23768?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##             master   #23768   +/-   ##
=========================================
  Coverage          ?   92.29%           
=========================================
  Files             ?      161           
  Lines             ?    51490           
  Branches          ?        0           
=========================================
  Hits              ?    47521           
  Misses            ?     3969           
  Partials          ?        0
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.68% <100%> (?)` | |
| #single | `42.32% <0%> (?)` | |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/23768?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/api/extensions/\_\_init\_\_.py](https://codecov.io/gh/pandas-dev/pandas/pull/23768/diff?src=pr&el=tree#diff-cGFuZGFzL2FwaS9leHRlbnNpb25zL19faW5pdF9fLnB5) | `100% <ø> (ø)` | |
| [pandas/util/\_decorators.py](https://codecov.io/gh/pandas-dev/pandas/pull/23768/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvX2RlY29yYXRvcnMucHk=) | `91.34% <100%> (ø)` | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23768?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/23768?src=pr&el=footer). Last update [6e932f8...bb8640f](https://codecov.io/gh/pandas-dev/pandas/pull/23768?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @WillAyd  Done with the changes. Please take a look again. I ran `scripts/validate_docstrings.py`,  i didn't introduce any docstring errors.  @WillAyd  Done @srinivasreddy looks like you have a travis failure on the code checks if you can take a look @WillAyd   I have seen the difference between failing travis job and successful one, but i couldn't find any difference.  Could you please help in figuring it? You've got a flake8 issue here in `pandas/util/_decorators.py` line 317 for being too long (can also check the flake8 error message above in thread).

 Done . Merge pls Thanks @srinivasreddy 