def METHOD_NAME(self):
    """
    ---
    description: find the number of sources with and without a Healpix value
    tags:
      - source
    responses:
        200:
          content:
            application/json:
              schema:
                allOf:
                  - $ref: '#/components/schemas/Success'
                  - type: object
                    properties:
                      data:
                        type: object
                        properties:
                          totalWithoutHealpix:
                            type: integer
                          totalWithHealpix:
                            type: integer
        400:
          content:
            application/json:
              schema: Error
    """
    with self.Session() as session:
        stmt = sa.select(Obj).where(Obj.healpix.is_(None))
        count_stmt = sa.select(func.count()).select_from(stmt.distinct())
        total_missing = session.execute(count_stmt).scalar()
        # get the number of Objs with Healpix
        stmt = sa.select(Obj).where(Obj.healpix.isnot(None))
        count_stmt = sa.select(func.count()).select_from(stmt.distinct())
        total_healpix = session.execute(count_stmt).scalar()
    results = {
        'totalWithoutHealpix': total_missing,
        'totalWithHealpix': total_healpix,
    }
    return self.success(data=results)