code: def engine_file(self):
          
          return os.path.join(self.ipython_dir,
                              'profile_{0}'.format(self.profile),
                              'security/ipcontroller-engine.json')
docs: Specify path to the ipcontroller-engine.json file.
  
          This file is stored in in the ipython_dir/profile folders.
  
          Returns :
                - str, File path to engine file