Firestore trigger 1 - send answer to Android Thing

FirestoreTrigger1.java

export const onAnswer = functions.firestore.document('/pic/{picId}').onUpdate(_onAnswer)
async function _onAnswer(change: functions.Change<DocumentSnapshot>): Promise<any> {
    const picId = change.before.id      "//20180624120000"
    const previous = change.before.data() as Pic
    const pic = change.after.data() as Pic

    // Only interested in pics that have a new answer
    if (previous.answer || !pic.answer) {
        console.log("This is not the update you are looking for.")
        return Promise.resolve()
    }
}
// cont'd...