code: def _check_search_kwarg_types(self, kwargs):
          '''Checks that every element of kwargs is a valid type in this tree.'''
          for key in kwargs:
              if key not in self.node_types:
                  raise TypeError("Invalid search type: {}".format(key)f _check_search_kwarg_types(self, kwargs):
          '''Checks that every element of kwargs is a valid type in this tree.'''
          for key in kwargs:
              if key not in self.node_types:
                  raise TypeError("Invalid search type: {}".format(key))
docs: Checks that every element of kwargs is a valid type in this tree.