code: public static Map<String, Set<ByteBuffer>> getRowDeletionMap(DBTransaction transaction) {
          Map<String, Set<ByteBuffer>> rowDeletionMap = new HashMap<>();
          for(RowDelete mutation: transaction.getRowDeletes()) {
              String storeName = mutation.getStoreName();
              String rowKey = mutation.getRowKey();
              Set<ByteBuffer> rows = rowDeletionMap.get(storeName);
              if(rows == null) {
                  rows = new HashSet<ByteBuffer>();
                  rowDeletionMap.put(storeName, rows);
              }
              rows.add(Utils.toByteBuffer(rowKey));
          }
          return rowDeletionMap;
      }
docs: ----- Cassandra-specific public methods