code: private Row row(DecoratedKey partitionKey, long timestamp) {
          QueryFilter queryFilter = QueryFilter.getIdentityFilter(partitionKey, metadata.cfName, timestamp);
          ColumnFamily columnFamily = baseCfs.getColumnFamily(queryFilter);
          if (columnFamily != null) {
              ColumnFamily cleanColumnFamily = cleanExpired(columnFamily, timestamp);
              return new Row(partitionKey, cleanColumnFamily);
          }
          return null;
      }
docs: Returns the CQL3 {@link Row} identified by the specified key pair, using the specified time stamp to ignore
  deleted columns. The {@link Row} is retrieved from the storage engine, so it involves IO operations.
  
  @param partitionKey The partition key.
  @param timestamp    The time stamp to ignore deleted columns.
  @return The CQL3 {@link Row} identified by the specified key pair.