code: def f(self, m):
          
          if len(self.children) == 0:
              return self._f(m)
          elif len(self.children) == 1:
              return self._f(m) and self.children[0].f(m)
          else:
              raise Exception(
                  f"{self.__name__} does not support more than one child Matcher"
              )
docs: The recursively composed version of filter function f.
          By default, returns logical **conjunction** of operator and single
          child operator