class_docstr: A directed graph that can easily be JSON serialized for visualization.
  
  When serializing, it generates the following fields:
    edge: The list of all serialized Edge instances.
    node: The list of all serialized Vertex instances.
code: def __init__(self):
      self.vertices = []
      self.edges = []
      self.vertex_map = {}
  
file_path: tensor2tensor/tensor2tensor/insights/graph.py
label_desc: Use image node_id 1 to create a new Graph object from inherited base classes: object with example: obj = Graph()