code: function changeHandler(eventOptions = {}) {
      const { key, silent } = eventOptions;
      const def = defs.get(this);
  
      if (key && key in def.keys && !silent) {
          triggerOne(this, 'set', eventOptions);
          triggerOne(this, 'modify', eventOptions);
      }
  }
docs: called on change triggers set and modify if data keys are changed