A |Length| value calculated from the values of `w:ind/@w:firstLine`
        and `w:ind/@w:hanging`. Returns |None| if the `w:ind` child is not
        present.

def first_line_indent(self):
        """
        A |Length| value calculated from the values of `w:ind/@w:firstLine`
        and `w:ind/@w:hanging`. Returns |None| if the `w:ind` child is not
        present.
        """
        ind = self.ind
        if ind is None:
            return None
        hanging = ind.hanging
        if hanging is not None:
            return Length(-hanging)
        firstLine = ind.firstLine
        if firstLine is None:
            return None
        return firstLine