[Haskell-beginners] How to use Text.Printf w/ custom types

Hello All! As I understand to use Text.Printf.printf with custom types or to return result as Text instead of String I must implement some class instances: PrintfType, PrintfArg. But how to do this if they are exported from module as type-names only - without its methods (i.e. not "Printf (..)", but "Printf") ? I tried to import Text.Printf.Internal but seems that no such submodule... Any ideas? === Best regards, Paul