code: def generate_string(converter, input, format='xml'):
      
      serializer = generator.new(format)
      if serializer is None:
          raise TypeError('invalid output format ' + repr(format))
      builder = Builder()
      converter.parse_string(input, builder)
      return builder.serialize(serializer)
docs: Like generate(), but reads the input from a string instead of
      from a file.
  
      :type  converter: compiler.Context
      :param converter: The compiled converter.
      :type  input: str
      :param input: The string to convert.
      :type  format: str
      :param format: The output format.
      :rtype:  str
      :return: The resulting output.