docs: function mergeInner(base, mixin, mergeArrays) {
      if (base === null || typeof base !== 'object' || Array.isArray(base)) {
          throw new Error('base must be object');
      }
      if (mixin === null || typeof mixin !== 'object' || Array.isArray(mixin)) {
          throw new Error('mixin must be object');
      }
      Object.keys(mixin).forEach((name) => {
          mergeHelper(base, mixin, name, mergeArrays);
      });
  }