code: public Set<String> getRegisteredAccountReservationKeysForCurrentThread() {
  		lock.lock();
  		try {
  			Map<MailAccount, String> accountsForThread = transformValues(filterValues(usedAccounts, new CurrentThreadWrapperPredicate()),
  					new Function<ThreadReservationKeyWrapper, String>() {
  						@Override
  						public String apply(final ThreadReservationKeyWrapper input) {
  							return input.accountReservationKey;
  						}
  					}
  			);
  
  			return ImmutableSet.copyOf(accountsForThread.values());
  		} finally {
  			lock.unlock();
  		}
  	}
docs: Gets the set of reservation key under which accounts are reserved for the current thread.
  
  @return the set of reservation keys