TypeError:不支持在下一个(<class“generator”)上调用

在以下代码中:

self.estimator = tf.estimator.DNNRegressor( ... )
...
predictions = self.estimator.predict(predict_features)
print("predictions: {}".format(type(predictions)))
while True:
  try:
    result = next(predictions)
    predict_labels.append(result)
  except StopIteration:
    return predict_labels

class 'generator' result = next(predictions) 在第0次迭代中生成了此异常:

TypeError: unsupported callable