Main function to control the action of the lasso, allows user to draw on data image and adjust thematic map
        :param verts: the vertices selected by the lasso
        :return: nothin, but update the selection array so lassoed region now has the selected theme, redraws canvas

def onlasso(self, verts):
        """
        Main function to control the action of the lasso, allows user to draw on data image and adjust thematic map
        :param verts: the vertices selected by the lasso
        :return: nothin, but update the selection array so lassoed region now has the selected theme, redraws canvas
        """
        p = path.Path(verts)
        ind = p.contains_points(self.pix, radius=1)
        self.history.append(self.selection_array.copy())
        self.selection_array = self.updateArray(self.selection_array,
                                                ind,
                                                self.solar_class_var.get())
        self.mask.set_data(self.selection_array)
        self.fig.canvas.draw_idle()