def visit_binop(self, node, parent):
        """visit a BinOp node by returning a fresh instance of it"""
        newnode = nodes.BinOp(
            self._bin_op_classes[type(node.op)], node.lineno, node.col_offset, parent
        )
        newnode.postinit(
            self.visit(node.left, newnode), self.visit(node.right, newnode)
        )
        return newnode
visit a BinOp node by returning a fresh instance of it