code: def child(self, local_name=None, name=None, ns_uri=None, node_type=None,
              filter_fn=None):
          
          return self.children(name=name, local_name=local_name, ns_uri=ns_uri,
              node_type=node_type, filter_fn=filter_fn, first_only=True)
docs: :return: the first child node matching the given constraints, or \
                   *None* if there are no matching child nodes.
  
          Delegates to :meth:`NodeList.filter`.