不了解此TypeError：+不支持的操作数类型：“ NoneType”和“ float”

Question

我遇到了不受支持的操作数类型错误。我知道这意味着我代码中的某个地方，我什么都不返回，但是我不知道。您能帮我解决这个问题吗？

def explain_anomalies(y, window_size, sigma=1.0):

    avg = moving_average(y, window_size).tolist()
    residual = y - avg

    std = np.std(residual)
    return {'standard_deviation': round(std, 3),
            'anomalies_dict': collections.OrderedDict([(index, y_i) for 
                                                       index, y_i, avg_i in 
    zip(count(), y, avg)
              if (y_i > avg_i + (sigma*std)) | (y_i < avg_i - (sigma*std))])}

错误：

File "C:/Users/tcckaya/Documents/python/Kurs/anomaly_detect_zip1.py", line 72, in <listcomp>
    if (y_i > avg_i + (sigma*std)) | (y_i < avg_i - (sigma*std))])}

TypeError: unsupported operand type(s) for +: 'NoneType' and 'float'