title: ValueError: all the input array dimensions except for the concatenation axis must match exactly
body: <p>l have the following numpy arrays that l want to concatenate using numpy.hstack(())</p>
  
  <pre><code>dim(train_frames1)=(2000, 1, 224, 224)
  dim(train_frames2)(1000, 1, 224, 224)
  dim(train_frames3)=(2000, 1, 224, 224)
  dim(train_frames4)=(2000, 1, 224, 224)
  dim(train_frames5)=(2000, 1, 224, 224)
  dim(train_frames6)=(586, 1, 224, 224)
  </code></pre>
  
  <p>l did the following :</p>
  
  <pre><code>import numpy as np
  train=np.hstack((train_frames1, train_frames2,train_frames3,train_frames4,train_frames5, train_frames6))
  </code></pre>
  
  <p>l get this error :</p>
  
  <pre><code>    return _nx.concatenate(arrs, 1)
  ValueError: all the input array dimensions except for the concatenation axis must match exactly
  </code></pre>