title: how to convert numpy array to keras tensor
body: <p>When using the keras model to do predict, I got the error below<br></p>
  <blockquote>
  <p>AttributeError: 'Tensor' object has no attribute 'ndim'</p>
  </blockquote>
  <p>The reason is that the weights is numpy array, not tensor.<br>
  So how to convert numpy array to keras tensor?</p>