old_contents: """This module contains the PDA implementation"""
  # !/usr/bin/python
  import imp
  from pdadiff import PdaDiff
  from alphabet import createalphabet
  
  try:
      print 'Checking for pythonpda module:',
      imp.find_module('pythonpda')
      print 'OK'
      from pythonpda import PythonPDA
  
      class PDA(PythonPDA):
          """This is the structure for a PDA"""
  
          def shortest_string(self):
              """
              Uses BFS in order to find the shortest string
              Args:
                  None
              Returns:
                  str: The shortest string
              """
              ops = PdaDiff(None, None, self.alphabet)
              ops.mmc = self
              return ops.get_string()
  
          def diff(self, mmb):
              """
              Automata Diff operation
              """
              ops = PdaDiff(self, mmb, self.alphabet)
              mmc = ops.diff()
              return mmc
  
  except ImportError:
      print 'FAIL'
new_contents: """This module contains the PDA implementation"""
  # !/usr/bin/python
  import imp
  from alphabet import createalphabet
  
  try:
      print 'Checking for pythonpda module:',
      print 'OK'
      from pythonpda import PythonPDA, PDAState
  
      class PDA(PythonPDA):
          """This is the structure for a PDA"""
  
          def shortest_string(self):
              """
              Uses BFS in order to find the shortest string
              Args:
                  None
              Returns:
                  str: The shortest string
              """
              from pdadiff import PdaDiff
              ops = PdaDiff(None, None, self.alphabet)
              ops.mmc = self
              return ops.get_string()
  
          def diff(self, mmb):
              """
              Automata Diff operation
              """
              from pdadiff import PdaDiff
              ops = PdaDiff(self, mmb, self.alphabet)
              mmc = ops.diff()
              return mmc
  
  except ImportError:
      print 'FAIL'
subject: remove pdadiff