Collection<Account> getAccounts() {
    return Collections.unmodifiableCollection(idToAccountMap.values());
  }
Gets all the {@link Account}s in this {@code AccountInfoMap} in a {@link Collection}.
@return A {@link Collection} of all the {@link Account}s in this map.
ambry-account/src/main/java/com/github/ambry/account/AccountInfoMap.java