def save(self, doc):
        if doc.id:
            return self.update(doc)
        else:
            return self.insert(doc)
def literal_eval(node_or_string):
    if isinstance(node_or_string, AST):
        node_or_string = gast_to_ast(node_or_string)
    return _ast.literal_eval(node_or_string)