if (conv2d_and_block_size.second != block_size) {
        argnum_and_convolutions.erase(arg_num);
        break;
      }
    }
  }

  // If there is no qualified space to depth transform.
  if (argnum_and_convolutions.empty()) {
    return;
  }

  // Apply space to depth transform.
  for (auto argnum_and_convolution : argnum_and_convolutions) {