code: def star(self, input_string):
          
          if input_string != self.epsilon and input_string != self.empty:
              return "(" + input_string + ")*"
          else:
              return ""
docs: Kleene star operation
          Args:
              input_string (str): The string that the kleene star will be made
          Returns:
              str: The applied Kleene star operation on the input string