code: function(seriesKeys) {
          var fieldValues = _.values(seriesKeys),
              matchingSeriesDef = _.find(this._attributes.series, function(seriesDef) {
                  return _.contains(fieldValues, seriesDef.name);
              });
          if (!matchingSeriesDef) {
              return _.find(this._attributes.series, function(seriesDef) {
                  return !seriesDef.name;
              });
          }
          return matchingSeriesDef;
      }
docs: returns a series def if the series def has a name value that matches one of the series keys.