input_shape[1], block_shape[0],
      ...,
      input_shape[M], block_shape[M-1],

      input_shape[M+1], ..., input_shape[N-1]]

3. Reshape `permuted` to produce `reshaped_permuted` of shape
     [batch / prod(block_shape),

      input_shape[1] * block_shape[0],
      ...,
      input_shape[M] * block_shape[M-1],

      input_shape[M+1],
      ...,
      input_shape[N-1]]