def _validate_graph_type(self, graph_type):
    if (graph_type not in ['instance', 'schema']):
        raise ValueError("graph_type can only be 'instance' or 'schema'")
def _validate_graph_type(self, graph_type):
    if (graph_type not in ['instance', 'schema']):
        raise ValueError("graph_type can only be 'instance' or 'schema'")