code: public function deleteByPrimaryKey($primaryKeyValue, ?string $returnField = null): ?string
      {
          $query = "DELETE FROM $this->tableName WHERE ".$this->getPrimaryKeyColumnName()." = $1";
          $q = new QueryBuilder($query, $primaryKeyValue);
  
          if ($returnField !== null) {
              return $q->executeWithReturnField($returnField);
          }
  
          $dbResult = $q->execute();
  
          if (pg_affected_rows($dbResult) == 0) {
              throw new Exceptions\QueryResultsNotFoundException();
          }
  
          return null;
      }
docs: if row is not deleted (ie primary key value not found), an exception is thrown
  note that $primaryKeyValue argument is untyped as it can be string or int