r"""Add all patterns from another replacer.

        All patterns and replacements from replacer are appended to the ones
        already defined.

def add_replacer(self, replacer):
        r"""Add all patterns from another replacer.

        All patterns and replacements from replacer are appended to the ones
        already defined.
        """
        self._pat = None
        self._pats.extend(replacer._pats)
        self._funs.extend(replacer._funs)