code: @Override
      public List<Values> mapToValues(String rowKey, Map<String, String> columns, Tuple input) {
          List<Values> values = new ArrayList<Values>();
          Set<String> vals = columns.keySet();
          for(String columnName : vals){
              if(this.isDrpc){
                  values.add(new Values(input.getValue(0), rowKey, columnName));
              } else {
                  values.add(new Values(rowKey, columnName));
              }
          }
          return values;
      }
docs: Given a set of columns, maps to values to emit.
  
  @param columns
  @return