How to fix 'KeyError: dtype('float32')' in LDAviz
I know this is late but I just fixed a similar problem by updating my gensim library from 3.4 to the current version which for me is 3.8.
I use LDAvis library to visualize my LDA topics. It works fine before, but it gets me this error when I download the saved model files from Sagemaker to the local computer. I don't know why does this happen? Does that relate to Sagemaker?
If I run from the local, and saved the model from local, and then run LDAviz library, it works fine.

KeyError                                  Traceback (most recent call last)
 in ()
~\AppData\Local\Continuum\anaconda3\lib\site-packages\pyLDAvis\gensim.py in prepare(topic_model, corpus, dictionary, doc_topic_dist, **kwargs)
    116     See pyLDAvis.prepare for **kwargs.
    117     """
--> 118     opts = fp.merge(_extract_data(topic_model, corpus, dictionary, doc_topic_dist), kwargs)
    119     return vis_prepare(**opts)
~\AppData\Local\Continuum\anaconda3\lib\site-packages\pyLDAvis\gensim.py in _extract_data(topic_model, corpus, dictionary, doc_topic_dists)
     46           gamma = topic_model.inference(corpus)
     47       else:
---> 48           gamma, _ = topic_model.inference(corpus)
     49       doc_topic_dists = gamma / gamma.sum(axis=1)[:, None]
     50    else:
~\AppData\Local\Continuum\anaconda3\lib\site-packages\gensim\models\ldamodel.py in inference(self, chunk, collect_sstats)
    665             # phinorm is the normalizer.
    666             # TODO treat zeros explicitly, instead of adding epsilon?
--> 667             eps = DTYPE_TO_EPS[self.dtype]
    668             phinorm = np.dot(expElogthetad, expElogbetad) + eps
    669 
KeyError: dtype('float32')