desert-bot

"type" is a very [overloaded](https://tratt.net/laurie/blog/entries/another_non_argument_in_type_systems.html) [term](https://mikeinnes.github.io/2020/05/19/types.html). We can use "class" to refer to Python classes to reduce some confusion.

https://github.com/marshmallow-code/marshmallow/pull/1702 deprecates `**metadata` in favor of `metadata=`.