title: Can't use sample_weights both for fit or evaluate model on Keras
body: <p>I need to set sample_weights parameter for training a unbalanced classes on Keras.</p>
  
  <p>If I try to use a list of weights it gives a error:
  AttributeError: 'list' object has no attribute 'shape'</p>
  
  <p>If I try to use a 1D array, it gives the error:
  ValueError: Found a sample_weight array with shape (17,) for an input with shape (180, 17). sample_weight cannot be broadcast.</p>
  
  <pre><code>model.evaluate(X, Y, batch_size=50, sample_weight=weights)
  </code></pre>
  
  <p>In the end of the day, any way I tried to pass this parameters it gives some error.</p>
  
  <p>Any ideas?</p>