code: @Nonnull
    @ReturnsMutableCopy
    public ICommonsList <String> getAllUserGroupIDsWithAssignedRole (@Nullable final String sRoleID)
    {
      if (StringHelper.hasNoText (sRoleID))
        return getNone ();
  
      return getAllMapped (aUserGroup -> aUserGroup.containsRoleID (sRoleID), IUserGroup::getID);
    }
docs: Get a collection of all user group IDs to which a certain role is assigned
  to.
  
  @param sRoleID
  The role ID to search
  @return A non-<code>null</code>but may be empty collection with all
  matching user group IDs.