Keras和Tensorflow:unbundlocalerror:赋值前引用的局部变量“self”

我正在学习TensorFlow和Keras的教程。

from keras.models import Sequential
from keras.layers import Dense

model = Sequential()

model.add(Dense(units=64, activation='relu', input_dim=100))
model.add(Dense(units=10, activation='softmax'))

(这不是完整的stacktrace,因为StackOverflow不允许我说它只有代码)

--------------------------------------------------------------------
UnboundLocalError                  Traceback (most recent call last)
<ipython-input-49-30ebc8793948> in <module>()
      5 from keras.layers import Dense
      6 
----> 7 model.add(Dense(units=64, activation='relu', input_dim=100))

--> 164                     layer(x)
    165                     set_inputs = True
    166                 else:


/usr/local/lib/python3.7/site-packages/keras/initializers.py in __call__(self, shape, dtype)
   self._message_listener.Modified()

UnboundLocalError: local variable 'self' referenced before assignment

这可能是因为Python3.7吗?