code: def minimumLabelWidth(self):
          
          min_w = 0
          metrics = QFontMetrics(self.labelFont())
          for label in self.labels():
              min_w = max(min_w, metrics.width(label))
          
          return max(self._minimumLabelWidth,
                     min_w + self.horizontalLabelPadding())
docs: Returns the minimum label width required on this renderers font size.
          
          :param      labels | [<str>, ..]