code: def add_response(self, response, value):
          
          if value != "stop":
              self.X = pd.concat([self.X, pd.DataFrame({"Signal":[value]})])
              self.y = np.array(list(self.y) + [response])
              if len(set(list(self.y))) > 1:
                  self.model = self.fit_model(self.X , self.y)
docs: Add response to staircase.
  
          Parameters
          ----------
          response : int or bool
              0 or 1.
          value : int or float
              Signal corresponding to response.