How to disable unicode beautification ('\' 'λ', 'forall' '∀', etc)

By default, yi beautifies haskell code. This code:

data ExtHL syntax = forall cache. ExtHL (Highlighter cache syntax)

looks like this (or worse, if your terminal doesn't like unicode):

data ExtHL syntax = ∀ cache· ExtHL (Highlighter cache syntax)

To disable this behavior, user has to provide modes without beautification. Here is an example config:

import qualified Yi.Mode.Haskell as Haskell

main :: IO ()
main = yi $ defaultVimConfig {
    modeTable = (myModes ++ modeTable defaultVimConfig)
}

myModes = [
         AnyMode Haskell.fastMode {
             -- I prefer ASCII
             modeGetAnnotations = (const . const) []
         }
    ]