docs: def drawAxis( self, painter ):
          """
          Draws the axis for this system.
          """
          # draw the axis lines
          pen = QPen(self.axisColor())
          pen.setWidth(4)
          painter.setPen(pen)
          painter.drawLines(self._buildData['axis_lines'])
          
          # draw the notches
          for rect, text in self._buildData['grid_h_notches']:
              painter.drawText(rect, Qt.AlignTop | Qt.AlignRight, text)
          
          for rect, text in self._buildData['grid_v_notches']:
              painter.drawText(rect, Qt.AlignCenter, text)