code: public UUID getId(String ksName, String cfName)
      {
          return cfIdMap.get(Pair.create(ksName, cfName));
      }
docs: Lookup keyspace/ColumnFamily identifier
  
  @param ksName The keyspace name
  @param cfName The ColumnFamily name
  
  @return The id for the given (ksname,cfname) pair, or null if it has been dropped.