code: def __init__(self, functions):
      self._orig = functions
      self._flags = {}
  
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 1 to create a new _TopologicalSort object  with example: obj = _TopologicalSort(functions)