code: @Override
      public List<Values> mapToValues(String rowKey, Map<String, String> columns, Tuple input) {
          List<Values> values = new ArrayList<Values>();
          String delimVal = columns.get(this.columnKeyField);
          if (delimVal != null) {
              String[] vals = delimVal.split(this.delimiter);
              for (String val : vals) {
                  if (this.isDrpc) {
                      values.add(new Values(input.getValue(0), rowKey, val));
                  } else {
                      values.add(new Values(rowKey, val));
                  }
              }
          }
          return values;
      }
docs: Given a set of columns, maps to values to emit.
  
  @param columns
  @return