Improve docs for option_option
Improve docs for option_option

Hint about using tri-state enums to replace legitimate uses of `Option<Option<_>>`
graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust