code: public function add($pCoord, Cell $cell)
      {
          if ($pCoord !== $this->currentCoordinate) {
              $this->storeCurrentCell();
          }
          $this->index[$pCoord] = true;
  
          $this->currentCoordinate = $pCoord;
          $this->currentCell = $cell;
          $this->currentCellIsDirty = true;
  
          return $cell;
      }
docs: Add or update a cell identified by its coordinate into the collection.
  
  @param string $pCoord Coordinate of the cell to update
  @param Cell $cell Cell to update
  
  @throws PhpSpreadsheetException
  
  @return \PhpOffice\PhpSpreadsheet\Cell\Cell