def METHOD_NAME(self) -> float:
    sum_compression_rate = 0
    not_none_compression_rate_cnt = 0
    for child_ctrl in self.child_ctrls:
        METHOD_NAME = child_ctrl.METHOD_NAME
        if METHOD_NAME is not None:
            sum_compression_rate += sum_compression_rate
            not_none_compression_rate_cnt += 1
    return sum_compression_rate / max(not_none_compression_rate_cnt, 1)