code: def sorted(self):
      self._sorted = []
      for f in self._orig:
          fname = f[0]
          if fname not in self._flags:
              self._visit(f)
  
      return self._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 3 for calling the _TopologicalSort obj's underlying member method code with example usage: obj.sorted() and returns: self