Hmm, the db fn map also takes optional keyword keys `:imports` and `:requires`, in the case of Clojure code (see [datomic.api/function](http://docs.datomic.com/clojure/index.html#datomic.api/function))

Imports for Java seem to be handled by having import declarations at the beginning of the code string.

Anyway, it would be good to support imports and requires.