docs: def serialize_ndarray_npy(o):
      """
      Serializes a :obj:`numpy.ndarray` using numpy's built-in :obj:`save` function.
      This produces totally unreadable (and very un-JSON-like) results (in "npy"
      format), but it's basically guaranteed to work in 100% of cases.
  
      Args:
          o (:obj:`numpy.ndarray`): :obj:`ndarray` to be serialized.
  
      Returns:
          A dictionary that can be passed to :obj:`json.dumps`.
      """
      with io.BytesIO() as f:
          np.save(f, o)
          f.seek(0)
          serialized = json.dumps(f.read().decode('latin-1'))
      return dict(
          _type='np.ndarray',
          npy=serialized)