random_binomial NotImplementedError

[zsong]

model.add(Embedding(max_features,
                    embedding_dims,
                    input_length=maxlen,
                    dropout=0.2))

This line throws this exception:

    train_ret = func(*args, **kwargs)
  File "env\lib\site-packages\keras\backend\mxnet_backend.py", line 3007, in random_binomial
    raise NotImplementedError
NotImplementedError