DocStrings are not the only way. If you are using Sphinx to generate documentation then you should read this.

Example

Here is something I want to talk about:: <-- Special syntax to mark code beginning

    def my_fn(foo, bar=True): # Code itself
        """A really useful function.

        Returns None
        """

There are a few ways to do it. I think the most sensible in your case would be .. code-block::

""" This is a module documentation

Use this module like this:

.. code-block:: python

   res = aFunction(something, goes, in)
   print(res.avalue)

"""

Notice the blank line between the directive and the code block - it must be there in order for the block to render properly.

Comparing your code with the docs, you are missing indentation and an empty line between the highlight and the actual code. It should be like this:

def foo():
    '''
    .. highlight:: python
    .. code-block:: python

        import sys
        ...
    '''