old_contents: class Node(object):
    def __init__(self):
      # Properties will go here!
  
new_contents: class Node(object):
    def __init__(self):
      # Node(s) from which this Node receives values
      self.inbound_nodes = inbound_nodes
      # Node(s) to which this Node passes values
      self.outbound_nodes = []
      # For each inbound Node here, add this Node as an outbound to that Node.
      for n in self.inbound_nodes:
        n.outbound_nodes.append(self)
  
subject: Initialize inbound and outbound Nodes of a Node