code: public function getCellIterator($startRow = 1, $endRow = null)
      {
          return new ColumnCellIterator($this->parent, $this->columnIndex, $startRow, $endRow);
      }
docs: Get cell iterator.
  
  @param int $startRow The row number at which to start iterating
  @param int $endRow Optionally, the row number at which to stop iterating
  
  @return ColumnCellIterator