Frames with multiple custom columns

Data.hs

{-# LANGUAGE ConstraintKinds, DataKinds, FlexibleContexts, GADTs,
             OverloadedStrings, PatternSynonyms, QuasiQuotes,
             ScopedTypeVariables, TemplateHaskell, TypeOperators,
             ViewPatterns #-}
{-# LANGUAGE FlexibleInstances #-}

module Data where

import           Control.Lens
import           Data.Readable
import qualified Data.Text as T
import           Frames
import           Frames.CSV
import           Pipes
import qualified Pipes.Prelude as P
import           Types

tableTypes'
  rowGen {rowTypeName = "Answer"
         ,columnUniverse = $(colQ ''MyColumns)}
  "data/raw-anon-v1-0.csv"

answerStream :: Producer Answer IO ()
answerStream = readTableOpt answerParser "data/raw-anon-v1-0.csv"

Types.hs

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE FlexibleInstances #-}

module Types where

import Data.Typeable
import Data.Text
import Frames
import Data.Readable
import Control.Monad
import Frames.InCore
import qualified Data.Vector as V

newtype NumericalAnswer = NumericalAnswer (Maybe Int) deriving (Show,Read,Eq,Ord,Typeable)
newtype SkillLevel = SkillLevel (Maybe Text) deriving (Show,Read,Eq,Ord,Typeable)

instance Readable NumericalAnswer where
  fromText t
    | t == "0" = return $ NumericalAnswer $ Just 0
    | t == "1" = return $ NumericalAnswer $ Just 1
    | t == "2" = return $ NumericalAnswer $ Just 2
    | t == "3" = return $ NumericalAnswer $ Just 3
    | t == "4" = return $ NumericalAnswer $ Just 4
    | t == "\"\"" || t == "Don't know" = return $ NumericalAnswer Nothing
    | otherwise = mzero

instance Readable SkillLevel where
  fromText t
    | t `elem` ["none","beginner","learning","competent","expert"] = return $ SkillLevel (Just t)
    | t == "\"\"" = return $ SkillLevel Nothing
    | otherwise = mzero

type instance VectorFor NumericalAnswer = V.Vector
type instance VectorFor SkillLevel = V.Vector

type MyColumns =  SkillLevel ': NumericalAnswer ': CommonColumns