def METHOD_NAME(self, n):
    ret = []
    for node in self.inputs:
        if n > 0:
            next_node = node.METHOD_NAME(n - 1)
            if next_node:
                ret.append(next_node)
        else:
            ret.append("*")
    if self.inputs:
        return self.op_type + "(" + ",".join(ret) + ")"
    return self.op_type + "()"