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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 _help_add_edge(self, u: BaseEntity, v: BaseEntity, attr: Mapping) -> str: """Help add a pre-built edge."""

        self.add_node_from_data(u)
        self.add_node_from_data(v)

        return self._help_add_edge_helper(u, v, attr)