parseFile :: FromJSON a => FilePath -> IO (Maybe a)
parseFile json_path = do
  transactions <- BS.readFile json_path
  return $ decode transactions

-- Exercise 4 -----------------------------------------
parseFile :: FromJSON a => FilePath -> IO (Maybe a)
parseFile json_path = do
  transactions <- BS.readFile json_path
  return $ decode transactions

-- Exercise 4 -----------------------------------------
parseFile json_path = do
  transactions <- BS.readFile json_path
  return $ decode transactions

-- Exercise 4 -----------------------------------------