docs: def produce_fake_hash(x):
      """
      Produce random, binary features, totally irrespective of the content of
      x, but in the same shape as x.
      """
      h = np.random.binomial(1, 0.5, (x.shape[0], 1024))
      packed = np.packbits(h, axis=-1).view(np.uint64)
      return zounds.ArrayWithUnits(
          packed, [x.dimensions[0], zounds.IdentityDimension()])