old_contents: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  #
  # Cache abstraction.
  #
  # Liang Wang @ Computer Lab, Cambridge University
  # 2015.06.15
  
  
  class Cache():
  
      def __init__(self, quota):
          self._quota = quota
          pass
  
  
      def add(self):
          pass
  
  
      def remove(self):
          pass
  
  
      def is_full(self):
          b = False
          return b
  
      pass
  
new_contents: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  #
  # Cache abstraction.
  #
  # Liang Wang @ Computer Lab, Cambridge University
  # 2015.06.15
  
  
  class Cache():
  
      def __init__(self, quota):
          """Init the cache."""
          self._quota = quota
          pass
  
  
      def add(self):
          """Add a new item to cache."""
          pass
  
  
      def remove(self):
          """Remove an item from cache."""
          pass
  
  
      def is_full(self):
          """Check if the cache is full."""
          b = False
          return b
  
      pass
  
subject: edit ...