Remove decorations added through set_extra_selections.

        Args:
            key (str) name of the extra selections group.

def clear_extra_selections(self, key):
        """Remove decorations added through set_extra_selections.

        Args:
            key (str) name of the extra selections group.
        """
        for decoration in self.extra_selections_dict.get(key, []):
            self.decorations.remove(decoration)
        self.extra_selections_dict[key] = []