 DOC: updated the docstring of Series.dot 
- [ ] closes #xxxx
- [ ] tests added / passed
- [x ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @HubertKl! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/core/series.py`](https://github.com/HubertKl/pandas/blob/7ff583914b022897212f819e75878ca9f68481c5/pandas/core/series.py) !

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22890?src=pr&el=h1) Report
> Merging [#22890](https://codecov.io/gh/pandas-dev/pandas/pull/22890?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/5551bcf9d297ea8a0aeffb70b17ae6730e8abf89?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/22890/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/22890?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #22890   +/-   ##
=======================================
  Coverage   92.19%   92.19%           
=======================================
  Files         169      169           
  Lines       50835    50835           
=======================================
  Hits        46868    46868           
  Misses       3967     3967
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.61% <ø> (ø)` | :arrow_up: |
| #single | `42.35% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/22890?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/22890/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `93.75% <ø> (ø)` | :arrow_up: |

------

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> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22890?src=pr&el=footer). Last update [5551bcf...887d72d](https://codecov.io/gh/pandas-dev/pandas/pull/22890?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Thanks @datapythonista  for the comments! I updated the pull request. 

I did check PEP8 with the command
git diff upstream/master -u -- "*.py" | flake8 --diff
but nothing came out of this. Maybe my PEP8 checker is not well configured... The thing with PEP-8, is that `flake8` by default checks the code (which makes sense). But in this case, the problem is not in "code", but in the content of a string. To validate this code you need to run `flake8 --doctests`. But the problem will be that as we're not yet validating it automatically, you won't only see the errors in your changes, but in all the file, and there can be many (I'm not sure when using `--diff`). Thanks for the advice, it looks even better now. I added the s @ other example. Thanks @HubertKl 