Verifies and returns relevant TensorFlow graph. If non-None graph were passed,
        the same graph is returned. Otherwise, nodes's graph is exposed and it is
        undefined the default TensorFlow graph is used.

        :param graph: TensorFlow graph or None. Default is None.
        :return: TensorFlow graph.

def enquire_graph(self, graph=None):
        """
        Verifies and returns relevant TensorFlow graph. If non-None graph were passed,
        the same graph is returned. Otherwise, nodes's graph is exposed and it is
        undefined the default TensorFlow graph is used.

        :param graph: TensorFlow graph or None. Default is None.
        :return: TensorFlow graph.
        """
        if graph is None:
            graph = self.root.graph if self.graph is None else self.graph
            if graph is None:
                graph = tf.get_default_graph()
        return graph