docs: def _generate_anchors(base_size, scales, aspect_ratios):
      """Generate anchor (reference) windows by enumerating aspect ratios X
      scales wrt a reference (0, 0, base_size - 1, base_size - 1) window.
      """
      anchor = np.array([1, 1, base_size, base_size], dtype=np.float) - 1
      anchors = _ratio_enum(anchor, aspect_ratios)
      anchors = np.vstack(
          [_scale_enum(anchors[i, :], scales) for i in range(anchors.shape[0])]
      )
      return torch.from_numpy(anchors)