code: def add_buttons(self, classification):
          
          # Note(IS): Until we have good behaviour, we will disable cancel
          # button.
          # Add 3 buttons: Restore default, Cancel, Save
  
          # Restore default button, only for continuous layer (with threshold)
          if self.layer_mode == layer_mode_continuous['key']:
              self.restore_default_button = QPushButton(tr('Restore Default'))
              self.restore_default_button.clicked.connect(partial(
                  self.restore_default_button_clicked,
                  classification=classification))
  
          # Cancel button
          # cancel_button = QPushButton(tr('Cancel'))
          # cancel_button.clicked.connect(self.cancel_button_clicked)
  
          # Save button
          self.save_button = QPushButton(tr('Save'))
          self.save_button.clicked.connect(
              partial(self.save_button_clicked, classification=classification))
  
          button_layout = QHBoxLayout()
          button_layout.addStretch(1)
          button_layout.addWidget(self.restore_default_button)
          button_layout.addWidget(self.save_button)
  
          button_layout.setStretch(0, 3)
          button_layout.setStretch(1, 1)
          button_layout.setStretch(2, 1)
          # button_layout.setStretch(3, 1)
  
          self.right_layout.addLayout(button_layout)
docs: Helper to setup 3 buttons.
  
          :param classification: The current classification.
          :type classification: dict