def add_unqualified_edge(self, u: BaseEntity, v: BaseEntity, relation: str) -> str:
        """Add a unique edge that has no annotations.

        :param u: The source node
        :param v: The target node
        :param relation: A relationship label from :mod:`pybel.constants`
        :return: The key for this edge (a unique hash)
        """
        attr = {RELATION: relation}
        return self._help_add_edge(u, v, attr)
def add_unqualified_edge ( self , u : BaseEntity , v : BaseEntity , relation : str ) -> str : attr = { RELATION : relation } return self . _help_add_edge ( u , v , attr )
Add a unique edge that has no annotations.

        :param u: The source node
        :param v: The target node
        :param relation: A relationship label from :mod:`pybel.constants`
        :return: The key for this edge (a unique hash)