code: function(err, results) {
          if (err) {
              callback(err);
              return;
          }
          
          var keyFrequency = parseInt(results[0]);
          var docFrequency = parseInt(results[1]);
          var keyDocFrequency = results[2];
  
          // ensure that key frequency is relative to the given document (when appropriate)
          if (id && results.length == 4) {
              keyFrequency = parseInt(results[3]);
          }
          var tf = 1 + (Math.log(keyFrequency) / Math.LN10);
          var idf = Math.log(docFrequency / keyDocFrequency) / Math.LN10;
  
          var result = {};
          result.key = key;
          result.rawtf = keyFrequency;
          result.df = keyDocFrequency;
          result.n = docFrequency;
          result.idf = idf;
          result.tf = tf;
          result.tfidf = tf * idf;
          callback(null, result);
      }
docs: Executes and handles results returned from the multi redis command below