Return documentation about the argument that an endpoint accepts.

def format_endpoint_argument_doc(argument):
    """Return documentation about the argument that an endpoint accepts."""
    doc = argument.doc_dict()

    # Trim the strings a bit
    doc['description'] = clean_description(py_doc_trim(doc['description']))
    details = doc.get('detailed_description', None)
    if details is not None:
        doc['detailed_description'] = clean_description(py_doc_trim(details))

    return doc