code: @ObjectiveCName("loadMembersWithGid:withLimit:withNext:")
      public Promise<GroupMembersSlice> loadMembers(int gid, int limit, byte[] next) {
          return modules.getGroupsModule().loadMembers(gid, limit, next);
      }
docs: Load async members
  
  @param gid   group id
  @param limit limit of loading
  @param next  optional cursor of next
  @return promise of members slice