def METHOD_NAME(self, qp: QtGui.QPainter):
    if len(self.data) == 0 and len(self.reference) == 0:
        return
    if self.span == 0:
        return
    pen = QtGui.QPen(Chart.color.sweep)
    pen.setWidth(self.dim.point)
    line_pen = QtGui.QPen(Chart.color.sweep)
    line_pen.setWidth(self.dim.line)
    highlighter = QtGui.QPen(QtGui.QColor(20, 0, 255))
    highlighter.setWidth(1)
    self._set_start_stop()
    # Draw bands if required
    if self.bands.enabled:
        self.drawBands(qp, self.fstart, self.fstop)
    self.drawFrequencyTicks(qp)
    self.drawData(qp, self.data, Chart.color.sweep)
    self.drawData(qp, self.reference, Chart.color.reference)
    self.drawMarkers(qp)