code: def _fdopen(self, *args, **kwargs):
          
          if not is_int_type(args[0]):
              raise TypeError('an integer is required')
          return FakeFileOpen(self.filesystem)(*args, **kwargs)
docs: Redirector to open() builtin function.
  
          Args:
              *args: Pass through args.
              **kwargs: Pass through kwargs.
  
          Returns:
              File object corresponding to file_des.
  
          Raises:
              TypeError: if file descriptor is not an integer.