Now it is clear!
Why you name your COLLECTION → “diamonds”, but giving it the following ID —> “contact01”?
I would reccommend never to do such unlogical designation, regarding your IDs.
When your Collection is called → Diamonds → then it should have also the same or similar ID → " Diamonds ", or " diamonds ", or something like that, but not → “contact01” → that makes absolutely no sense.
And if you will have about 20-DBs in your project? Than you will go crazy!
So in your case → you used the wrong ID, or better said, you used the name of the collection instead of it’s ID!
You will surely have to RECREATE your DATABASE, until it is not to late.
Setup your IDs right from the beginning in a systematic and logical way and you won’t have any headaches later!