update method
Updates data on the document. Data will be merged with any existing document data.
Objects key can be a String or a FieldPath.
return id
Implementation
Future<String> update(Map<String, dynamic> data) async {
try {
await _reference.update(data);
} on FirebaseException catch (e) {
if (e.code == 'not-found') {
await _reference.set({});
await _reference.update(data);
} else {
rethrow;
}
}
final id = getID();
return id;
}