code: def set_XY(self, X, Y):
          
          self.update_model(False)
          self.set_Y(Y)
          self.set_X(X)
          self.update_model(True)
docs: Set the input / output data of the model
          This is useful if we wish to change our existing data but maintain the same model
  
          :param X: input observations
          :type X: np.ndarray
          :param Y: output observations
          :type Y: np.ndarray or ObsAr