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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 find_substring_edge(self, substring, suffix_tree_id):
 """Returns an edge that matches the given substring. """

        suffix_tree = self.suffix_tree_repo[suffix_tree_id]
        started = datetime.datetime.now()
        edge, ln = find_substring_edge(substring=substring, suffix_tree=suffix_tree, edge_repo=self.edge_repo)
        # if edge is not None:
        #     print("Got edge for substring '{}': {}".format(substring, edge))
        # else:
        #     print("No edge for substring '{}'".format(substring))
        print(" - searched for edge in {} for substring: '{}'".format(datetime.datetime.now() - started, substring))
        return edge, ln