static deepAssign(target, ...sources) {
    for (let source of sources) {
      for (let k in source) {
        const vs = source[k];
        const vt = target[k];
        if (Object(vs) == vs && Object(vt) === vt) {
          target[k] = _TiBaseComponent.deepAssign(vt, vs);
          continue;
        }
        target[k] = source[k];
      }
    }
    return target;
  }
Utility object deep merge fn
@param {object} target Merge target object
@param  {...object} sources 1 or more source objects to merge
@returns {object} Deep merged object