Import model GraphDef into the current graph.

def import_graph(self, t_input=None, scope='import', forget_xy_shape=True):
    """Import model GraphDef into the current graph."""
    graph = tf.get_default_graph()
    assert graph.unique_name(scope, False) == scope, (
        'Scope "%s" already exists. Provide explicit scope names when '
        'importing multiple instances of the model.') % scope
    t_input, t_prep_input = self.create_input(t_input, forget_xy_shape)
    tf.import_graph_def(
        self.graph_def, {self.input_name: t_prep_input}, name=scope)
    self.post_import(scope)