def _build_feature_trie(self):
        """
        Build the feature trie by adding the target features and their dependencies recursively.
        """
        feature_trie = Trie(
            default=lambda: (False, set(), set()),
            path_constructor=RelationshipPath,
        )

        for f in self.target_features:
            self._add_feature_to_trie(feature_trie, f, self.approximate_feature_trie)

        return feature_trie

        Build the feature trie by adding the target features and their dependencies recursively.
        
featuretools/computational_backends/feature_set.py