def runBF[T](bf: BatchFetchable[T]): T = {
  val entities = Entities(
    users = getManyUsersFromDb(bf.keys.users),
    groups = getManyGroupsFromDb(bf.keys,groups),
    posts = getManyPostsFromDb(bf.keys.posts),
    msgs = getManyMsgsFromDb(bf.keys.msgs)
  )
  bf.run(entities)
}