请查看以下代码行: https://github.com/gaearon/dnd-core/blob/master/src/actions/dragDrop.js#L16
export function beginDrag(sourceIds, {
publishSource = true,
clientOffset = null,
getSourceClientOffset
}: options = {}) { console.log('foo'); }
这里的冒号是什么样的ES6语法?