code: def set_string(self, option, value):
          
          if not isinstance(value, str):
              raise TypeError("%s must be a string" % option)
  
          self.options[option] = value
docs: Set a string option.
  
              Args:
                  option (str): name of option.
                  value (str): value of the option.
  
              Raises:
                  TypeError: Value must be a string.