Returns a suffix tree entity, equipped with node and edge repos it (at least at the moment) needs.

def get_suffix_tree(self, suffix_tree_id):
        """Returns a suffix tree entity, equipped with node and edge repos it (at least at the moment) needs.
        """
        suffix_tree = self.suffix_tree_repo[suffix_tree_id]
        assert isinstance(suffix_tree, GeneralizedSuffixTree)
        suffix_tree._node_repo = self.node_repo
        suffix_tree._node_child_collection_repo = self.node_child_collection_repo
        suffix_tree._edge_repo = self.edge_repo
        suffix_tree._stringid_collection_repo = self.stringid_collection_repo
        return suffix_tree