src/main/java/com/conveyal/gtfs/graphql/fetchers/RowCountFetcher.java
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();
    }
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();
    }
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