public Collection<Account> getAllAccountsHelper() {
    infoMapLock.readLock().lock();
    try {
      return accountInfoMapRef.get().getAccounts();
    } finally {
      infoMapLock.readLock().unlock();
    }
  }
Gets all the {@link Account}s in this {@code AccountService}. The {@link Account}s <em>MUST</em> have their
ids and names one-to-one mapped.
@return A collection of {@link Account}s.
ambry-account/src/main/java/com/github/ambry/account/CachedAccountService.java