KeyRange.bound 构造函数
实现
factory KeyRange.bound(/*Key*/ lower, /*Key*/ upper,
[bool lowerOpen = false, bool upperOpen = false]) =>
_KeyRangeFactoryProvider.createKeyRange_bound(
lower, upper, lowerOpen, upperOpen);
factory KeyRange.bound(/*Key*/ lower, /*Key*/ upper,
[bool lowerOpen = false, bool upperOpen = false]) =>
_KeyRangeFactoryProvider.createKeyRange_bound(
lower, upper, lowerOpen, upperOpen);