callGraph' f (TETag ty id args)                          = do
  argGraphs <- mapM (callGraph' f) args
  return $ concat argGraphs
callGraph' f (TETag ty id args)                          = do
  argGraphs <- mapM (callGraph' f) args
  return $ concat argGraphs
callGraph' f (TETag ty id args)                          = do
  argGraphs <- mapM (callGraph' f) args
  return $ concat argGraphs