code: public function insertNewColumnBefore($pBefore, $pNumCols = 1)
      {
          if (!is_numeric($pBefore)) {
              $objReferenceHelper = ReferenceHelper::getInstance();
              $objReferenceHelper->insertNewBefore($pBefore . '1', $pNumCols, 0, $this);
          } else {
              throw new Exception('Column references should not be numeric.');
          }
  
          return $this;
      }
docs: Insert a new column, updating all possible related data.
  
  @param int $pBefore Insert before this one, eg: 'A'
  @param int $pNumCols Number of columns to insert
  
  @throws Exception
  
  @return Worksheet