code: def _get_src_permutation_idx(indices):
      batch_idx = paddle.concat(
          [
              paddle.full_like(src, i)
              for i, (src, _) in enumerate(indices)
          ]
      )
      src_idx = paddle.concat([src for (src, _) in indices])
      return batch_idx, src_idx
  
file_path: PaddleDetection/ppdet/modeling/losses/queryinst_loss.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import paddle
  import paddle.nn.functional
  from ppdet.core.workspace import register
  from ppdet.modeling.losses.iou_loss import GIoULoss
  from .sparsercnn_loss import HungarianMatcher
label_desc: Use image node_id 5 for calling the QueryInstLoss obj's underlying member method code with example usage: obj._get_src_permutation_idx(indices) and returns: batch_idx,  src_idx