Does anybody know how to create a new firestore document with a nested aray?

what is wrong with this. there is absolutely no docs anywhere on how to do this.

{“fields”: { “bids”: { “arrayValue”: {“values”: [ { “mapValue”: { “bid”: {“doubleValue”: pageVars.newBidObject.bid }, “promoId”: { “stringValue”: pageVars.newBidObject.promoId } }} ] }}}}