docs: private boolean fileContains(File file, IGroupMember member) throws GroupsException {
          Collection ids = null;
          try {
              ids = member.isGroup() ? getGroupIdsFromFile(file) : getEntityIdsFromFile(file);
          } catch (Exception ex) {
              throw new GroupsException("Error retrieving ids from file", ex);
          }
          return ids.contains(member.getKey());
      }