code: public RepairFuture submitRepairSession(UUID parentRepairSession, Range<Token> range, String keyspace, RepairParallelism parallelismDegree, Set<InetAddress> endpoints, String... cfnames)
      {
          if (cfnames.length == 0)
              return null;
          RepairSession session = new RepairSession(parentRepairSession, range, keyspace, parallelismDegree, endpoints, cfnames);
          if (session.endpoints.isEmpty())
              return null;
          RepairFuture futureTask = new RepairFuture(session);
          executor.execute(futureTask);
          return futureTask;
      }
docs: Requests repairs for the given keyspace and column families.
  
  @return Future for asynchronous call or null if there is no need to repair