code: public static GraphQLFieldDefinition groupedField(String tableName, String groupByColumn) {
          return newFieldDefinition()
                  .name(groupByColumn)
                  .type(groupCountType)
                  .argument(stringArg("pattern_id"))
                  .type(new GraphQLList(groupCountType))
                  .dataFetcher(new RowCountFetcher(tableName, null, groupByColumn))
                  .build();
      }
docs: A GraphQL field used to deliver lists of group counts. Currently the primary use of this field is for delivering
  trip counts grouped by either service_id, pattern_id, or route_id. These quantities can also be filtered by
  providing a string value for pattern_id