code: function(opSet, target) {
          var self = this;
          AV._objectEach(opSet, function(change, key) {
            const [value, actualTarget, actualKey] = findValue(target, key);
            setValue(target, key, change._estimate(value, self, key));
            if (actualTarget && actualTarget[actualKey] === AV.Op._UNSET) {
              delete actualTarget[actualKey];
            }
          });
        }
docs: Applies the set of AV.Op in opSet to the object target.
  @private