def clear(self):
        """Clear the widget state."""
        self.results = None
        self.plot.clear()
        self.classifier_names = []
        self.selected_classifiers = []
        self.target_cb.clear()
        self.target_index = 0
        self.colors = []
        self._curve_data = {}
        self._plot_curves = {}
        self._rocch = None
        self._perf_line = None