module NSWTopo::ArcGIS::Statistics

def classify(*fields)
  statistics = fields.map.with_index do |name, index|
    { statisticType: "count", onStatisticField: name, outStatisticFieldName: "COUNT_#{index}" }
  end
  field_counts = get_json "#{@id}/query", **base_query, outStatistics: statistics.to_json, groupByFieldsForStatistics: fields.join(?,)
  field_counts["features"].map do |feature|
    [feature["attributes"].slice(*fields), feature["attributes"]["COUNT_0"]]
  end
end