docs: function getCombination (dateFilter, resolutionFilter, dataTypeFilter) {
    var c = {
      date: getFilter(date, dateFilter),
      resolution: getFilter(resolution, resolutionFilter),
      dataType: getFilter(dataType, dataTypeFilter),
      searchParameters: getSearchParameters(dateFilter, resolutionFilter, dataTypeFilter)
    };
    c.key = [c.date.key, c.resolution.key, c.dataType.key].join('_');
  
    return c;
  }