code: def setColumns( self, columns ):
          
          self.treeWidget().setColumns(columns)
          item = self.treeWidget().headerItem()
          for i in range(item.columnCount()):
              item.setTextAlignment(i, Qt.AlignBottom | Qt.AlignHCenter)
docs: Sets the columns for this gantt widget's tree to the inputed list of
          columns.
          
          :param      columns | {<str>, ..]