old_contents: #!/usr/bin/env python
  from __future__ import print_function
  from __future__ import unicode_literals
  
  
  class Node(object):
      ''' Create node element with default previous pointer. '''
      def __init__(self, value, next=None):
          ''' Previous pointer default to none. '''
          self.val = value
          self.next = next
  
  
  class Graph(object):
      ''' Create an empty linked list. '''
      def __init__(self):
          self.head = None
  
      def nodes():
          return nodes
  
      def edges():
          return edges
  
      def add_node(value):
          return
  
      def add_edge(value1, value2):
          return
  
      def del_node(value):
          return
  
      def has_node(value):
          return
  
      def neighbors(value):
          return neighbors
  
      def adjecent(value, value2):
          return condition
  
new_contents: #!/usr/bin/env python
  from __future__ import print_function
  from __future__ import unicode_literals
  
  
  class Graph(object):
      ''' Create an empty graph. '''
      def __init__(self):
          self.head = None
  
      def nodes():
          return nodes
  
      def edges():
          return edges
  
      def add_node(value):
          return
  
      def add_edge(value1, value2):
          return
  
      def del_node(value):
          return
  
      def has_node(value):
          return
  
      def neighbors(value):
          return neighbors
  
      def adjecent(value, value2):
          return condition
  
subject: delete unecessary code.