code: def open(self, filename):
          
          filename = self.real_filename(filename)
  
          if not os.path.exists(filename):
              raise self.FileNotFound(filename)
  
          with codecs.open(filename, encoding='utf-8') as f:
              yield f
docs: Yield a file-like object for file `filename`.
  
          This function is a context manager.