code: public void putNext(Tuple t) throws IOException
      {
          if (t.size() < 1)
          {
              // simply nothing here, we can't even delete without a key
              logger.warn("Empty output skipped, filter empty tuples to suppress this warning");
              return;
          }
  
          if (t.getType(0) == DataType.TUPLE)
          {
              if (t.getType(1) == DataType.TUPLE)
              {
                  Map<String, ByteBuffer> key = tupleToKeyMap((Tuple)t.get(0));
                  cqlQueryFromTuple(key, t, 1);
              }
              else
                  throw new IOException("Second argument in output must be a tuple");
          }
          else
              throw new IOException("First argument in output must be a tuple");
      }
docs: output: (((name, value), (name, value)), (value ... value), (value...value))