code: def _sort_functions(self, orig_functions):
      return _TopologicalSort(orig_functions).sorted()
  
file_path: nnabla/python/test/core/legacy_expander.py
imports: import collections
  import re
  from nnabla.utils import nnabla_pb2
label_desc: Use image node_id 4 for calling the NnpExpander obj's underlying member method code with example usage: obj._sort_functions(orig_functions) and returns: _TopologicalSort