title: unable to get length of items in .npy file
body: <p>I have a .npy file <a href="https://github.com/SharhadBashar/SC-CAM/blob/master/voc12/cls_labels.npy" rel="nofollow noreferrer">here</a></p>
  <p>Its just a file with an object that is a list of images and their labels. for example:</p>
  <pre><code>{
  '2007_002760': array([0., 0., 0., 0., 0., 0., 0., 1., 0., 0., 0., 0., 0., 0., 0., 0., 0.,0., 0., 0.], dtype=float32), 
  '2008_004036': array([0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 1., 1., 0., 0.,0., 0., 0.], dtype=float32)
  }
  </code></pre>
  <p>I want to open the file and get its length, and then possibly add to it or modify it</p>
  <p>I am able to open the file, but I cant get the length of items in it.
  Heres how i open it:</p>
  <pre><code>import numpy as np
  file = np.load('cls_labels.npy', allow_pickle = True)
  print(file.size)
  </code></pre>
  <p>What am I missing here?</p>