code: def _flat_to_list(flat, indices, B):
      array_list = []
      for i in range(B):
          array = flat[indices == i]
          if len(array) > 0:
              array_list.append(array)
          else:
              array_list.append(None)
      return array_list
  
file_path: chainercv/chainercv/links/model/fpn/faster_rcnn.py
imports: from __future__ import division
  import numpy
  import chainer
  from chainer.backends import cuda
  import chainer.functions
  from chainercv.links.model.fpn.misc import scale_img
label_desc: Use image node_id 2 for calling a global function with example usage: _flat_to_list(flat, indices, B) and returns: array_list