code: @Override
      public Map<String, String> mapToColumns(Tuple tuple) {
          Fields fields = tuple.getFields();
          Map<String, String> columns = new HashMap<String, String>();
          for (int i = 0; i < fields.size(); i++) {
              String name = fields.get(i);
              Object value = tuple.getValueByField(name);
              columns.put(name, (value != null ? value.toString() : ""));
          }
          return columns;
      }
docs: Default behavior is to write each value in the tuple as a key:value pair
  in the Cassandra row.
  
  @param tuple
  @return