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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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)