How do I create typeORM query utilityHelpers?

Question

I'm trying to migrate an existing RAW query to use typeORM's queryBuilder. For this I'm creating a class called utilityHelpers which contains methods that returns subqueries.

So far the code looks like this:

// Main query

const x = await this.createQueryBuilder('user')
    .select([
          ...utilityHelpers.getUserListPageColumns(),
    ])
    .leftJoin(utilityHelpers.getUserListAssociatedGroups(schoolId), 'gr', 'true')
        .leftJoin(utilityHelpers.getUserListAssociatedAcademies(schoolId), 'user_ac', 'true')
        .leftJoin(utilityHelpers.getUserListAssociatedFormVariants(), 'fv', 'true')
    .leftJoin(utilityHelpers.getUserListAssociatedReferrers(), 'referrers', 'true')
    .leftJoin(utilityHelpers.getUserListAssociatedUserStages(schoolId), 'userStages', 'true')
    .leftJoin(utilityHelpers.getUserListAssociatedCountry(), 'userCountry', 'true')
    .where(utilityHelpers.getWhereUserIsNew(filtersDictionary, schoolId))
    .getRawOne()

This is the helper:

// utilityHelpers

class UtilityHelper {
  // some code here
 
  public class getWhereUserIsNew(filters: filters, schoolId: string) {
      const filter = filters.isNew;

      if(!filter || filter?.value === 'all') return '';

      const subQuery = getRepository('userSchool')
      .createQueryBuilder('user_school')
      .where('"user_school"."isNew" = :isNewValue', { isNewValue: filter.value })
      .andWhere('"user_school"."userId" = "user"."id"')
        
      if (schoolId === 'all') {
      subQuery.andWhere('"user_school"."schoolId" = :schoolId', { schoolId });
      }

      const rawQuery = subQuery.getSql();
      subQuery.getQuery = () => `EXISTS (${rawQuery})`;

      return subQuery;
  }


  // other code
}

When I use this helper in my main query I get this error:

   name: EntityColumnNotFound
   message: No entity column "parameterIndex" was found.