Added entry for typestring parser check tool (#1402)

* Added typestring parser checker

* Updated some errors

* Update

* Checking if installation wokrs

* Trying again

* Updates

* Another Update

* Update pyproject.toml

* Update documentation.rst

* Update requirements.txt

* Update

* syntax highlighting should work?

* Update

* Reverted back

* Will this work?

* Update

* Still trying

* Update

* Update again

* Fixed the indentation issues

* Update

* updated code block

* Update again

* Update

* Update again with blackendocs

* Update documentation.rst

* Added skip option to doctests

* Added the link

* Update link

docs/source/contributing/documentation.rst

@@ -400,6 +400,25 @@ elements that are either a ``str`` or ``None``;
 ``(str, int)``; ``Tuple[:class:`int`, ...]`` for a tuple of variable
 length with only integers.
 
+.. note::
+   As a helper for tool for typesets, you can use `typestring-parser
+   <https://github.com/Dominik1123/typestring-parser>`_ 
+   which can be accessed by first installing it via ``pip`` - ``pip install typestring-parser`` and
+   then using ``from typestring_parser import parse``.
+
+.. doctest::
+    :options: +SKIP
+
+    >>> from typestring_parser import parse
+    >>> parse("int")
+    <class 'int'>
+    >>> parse("int or str")
+    typing.Union[int, str]
+    >>> parse("list of str or str")
+    typing.Union[typing.List[str], str]
+    >>> parse("list of (int, str)")
+    typing.List[typing.Tuple[int, str]]
+
 
 Adding type hints to functions and parameters
 ---------------------------------------------