code: public function getComment($pCellCoordinate)
      {
          // Uppercase coordinate
          $pCellCoordinate = strtoupper($pCellCoordinate);
  
          if (Coordinate::coordinateIsRange($pCellCoordinate)) {
              throw new Exception('Cell coordinate string can not be a range of cells.');
          } elseif (strpos($pCellCoordinate, '$') !== false) {
              throw new Exception('Cell coordinate string must not be absolute.');
          } elseif ($pCellCoordinate == '') {
              throw new Exception('Cell coordinate can not be zero-length string.');
          }
  
          // Check if we already have a comment for this cell.
          if (isset($this->comments[$pCellCoordinate])) {
              return $this->comments[$pCellCoordinate];
          }
  
          // If not, create a new comment.
          $newComment = new Comment();
          $this->comments[$pCellCoordinate] = $newComment;
  
          return $newComment;
      }
docs: Get comment for cell.
  
  @param string $pCellCoordinate Cell coordinate to get comment for, eg: 'A1'
  
  @throws Exception
  
  @return Comment