Edit current scheme.

def edit_scheme(self):
        """Edit current scheme."""
        dlg = self.scheme_editor_dialog
        dlg.set_scheme(self.current_scheme)

        if dlg.exec_():
            # Update temp scheme to reflect instant edits on the preview
            temporal_color_scheme = dlg.get_edited_color_scheme()
            for key in temporal_color_scheme:
                option = "temp/{0}".format(key)
                value = temporal_color_scheme[key]
                self.set_option(option, value)
            self.update_preview(scheme_name='temp')