def merge_section(key, prnt_sec, child_sec):
    """ Synthesize a output numpy docstring section.

    Parameters
    ----------
    key: str
        The numpy-section being merged.
    prnt_sec: Optional[str]
        The docstring section from the parent's attribute.
    child_sec: Optional[str]
        The docstring section from the child's attribute.
    Returns
    -------
    Optional[str]
        The output docstring section."""
    if prnt_sec is None and child_sec is None:
        return None
    if key == 'Short Summary':
        header = ''
    else:
        header = '\n'.join((key, ''.join('-' for i in range(len(key))), ''))
    if child_sec is None:
        body = prnt_sec
    else:
        body = child_sec
    return header + body
