def dependency_list(self, tkn: str) -> List[str]:
        """Return a list all of the grammarelts that depend on tkn

        :param tkn: 
        :return:
        """
        if tkn not in self.dependency_map:
            self.dependency_map[tkn] = [tkn]        # Force a circular reference
            self.dependency_map[tkn] = self.reference(tkn).dependency_list()
        return self.dependency_map[tkn]
Return a list all of the grammarelts that depend on tkn

        :param tkn: 
        :return: