code: def add_final_state(self, f):
  
          
          if f not in self.Q:
              LOG.error("The specified value is invalid, f must be a member of Q")
              raise InputError("The specified value is invalid, f must be a member of Q")
  
          self.F.add(f)
docs: :param f: int , the state qi to be added to F, epsilon is
          conventionally defined as the last node (q_|S|)