code: public Query range(ByteString start, ByteString end) {
      RowRange.Builder rangeBuilder = RowRange.newBuilder();
      if (start != null) {
        rangeBuilder.setStartKeyClosed(start);
      }
      if (end != null) {
        rangeBuilder.setEndKeyOpen(end);
      }
      builder.getRowsBuilder().addRowRanges(rangeBuilder.build());
      return this;
    }
docs: Adds a range to be looked up.
  
  @param start The beginning of the range (inclusive). Can be null to represent negative
  infinity.
  @param end The end of the range (exclusive). Can be null to represent positive infinity.