code: def __init__(self, model):
      # key: layer_name    value: keras layer
      self.layer_map = collections.OrderedDict()
      self.input_layers = list()
      self.output_layers = list()
      self.layer_name_map = collections.OrderedDict()
      self.topological_sort = list()
      self.model = model
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import collections
label_desc: Use image node_id 1 to create a new Graph object from inherited base classes: object with example: obj = Graph(model)