code: def format(tokens, formatter, outfile=None):  # pylint: disable=redefined-builtin
      
      try:
          if not outfile:
              realoutfile = getattr(formatter, 'encoding', None) and BytesIO() or StringIO()
              formatter.format(tokens, realoutfile)
              return realoutfile.getvalue()
          else:
              formatter.format(tokens, outfile)
      except TypeError as err:
          if (isinstance(err.args[0], str) and
              ('unbound method format' in err.args[0] or
               'missing 1 required positional argument' in err.args[0])):
              raise TypeError('format() argument must be a formatter instance, '
                              'not a class')
          raise
docs: Format a tokenlist ``tokens`` with the formatter ``formatter``.
  
      If ``outfile`` is given and a valid file object (an object
      with a ``write`` method), the result will be written to it, otherwise
      it is returned as a string.