from textwrap import dedent


def split_docstring(docstring):
    """
    Split a docstring into a summary and a description.

    Arguments:
        docstring (str): the docstring

    Returns:
        summary (str or None): a one-line summary.
        description (str or None): the multi-line description.
    """
    summary = None
    description = None
    if docstring:
        doc_lines = docstring.strip().split("\n")
        if doc_lines:
            summary = doc_lines[0].strip()
        if len(doc_lines) > 1:
            description = dedent("\n".join(doc_lines[1:]))
    return summary, description