Is there a way to map camel case fields using gatsby-source-firestore?

Question

I'm using gatsby-source-firestore and mapping fields from Firestore. When I map a field named createdAt, I don't see it in the GraphiQL interface. But when I change it to be createdat in Firestore and in the mapping (not using camel case), it does work. I wonder why it's happening, and if there's another way to make it work except for not using camel case in field names in Firestore (nothing regarding camel case is mentioned in their best practices documentation) or in gatsby-source-firestore repo.