Presence of `Raises` section on Numpy docstring causes obscure error when compiling docs

[bamford]

If a docstring is in Numpy format and contains a Raises section, which is part of the standard, the quarto-ghp GitHub Action crashes with an obscure error and long traceback.

The key part of the error is this:

File "/opt/hostedtoolcache/Python/3.12.9/x64/lib/python3.12/site-packages/fastcore/docscrape.py", line 112, in __init__
    for section in SECTIONS: self[section] = dedent_lines(self[section], split=False)
                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.12.9/x64/lib/python3.12/site-packages/fastcore/docscrape.py", line 235, in dedent_lines
    res = textwrap.dedent("\n".join(lines))
                          ^^^^^^^^^^^^^^^^
TypeError: sequence item 0: expected str instance, Parameter found

Here's a MWE docstring:

"""Do something.

    Does some stuff.

    Parameters
    ----------
    a : str
        A string argument.
    b : int, optional
        An optional integer argument.

    Raises
    ------
    ValueError
        If something is wrong with the provided parameters.
"""

Removing the Raises section solves the error, but it took a while to track down that this was the issue.

I know the preferred documenting format for nbdev is docments, but sometimes contributors write Numpy-style docstrings. It would be nice to avoid Raises sections from breaking the doc generation, or at least provide a more helpful error message.

Note that running show_doc manually in the notebook results in a UserWarning, so I don't understand why in the Action generates an exception.

I'm not sure exactly where the fix for this belongs (e.g. fastcore, workflows, ...), so starting by posting it here. The fix isn't urgent, but hopefully documenting this issue will help others who encounter it.

Many thanks to the nbdev team for providing such a valuable tool!