code: private function mapBorderStyle($borderStyle)
      {
          switch ($borderStyle) {
              case Border::BORDER_NONE:
                  return 'none';
              case Border::BORDER_DASHDOT:
                  return '1px dashed';
              case Border::BORDER_DASHDOTDOT:
                  return '1px dotted';
              case Border::BORDER_DASHED:
                  return '1px dashed';
              case Border::BORDER_DOTTED:
                  return '1px dotted';
              case Border::BORDER_DOUBLE:
                  return '3px double';
              case Border::BORDER_HAIR:
                  return '1px solid';
              case Border::BORDER_MEDIUM:
                  return '2px solid';
              case Border::BORDER_MEDIUMDASHDOT:
                  return '2px dashed';
              case Border::BORDER_MEDIUMDASHDOTDOT:
                  return '2px dotted';
              case Border::BORDER_MEDIUMDASHED:
                  return '2px dashed';
              case Border::BORDER_SLANTDASHDOT:
                  return '2px dashed';
              case Border::BORDER_THICK:
                  return '3px solid';
              case Border::BORDER_THIN:
                  return '1px solid';
              default:
                  // map others to thin
                  return '1px solid';
          }
      }
docs: Map border style.
  
  @param int $borderStyle Sheet index
  
  @return string