def _remove_extensions(self, extensions):
        grouped = defaultdict(set)
        for extension in extensions:
            ext_id = extension.qualified_id
            if ext_id not in self._extensions:
                msg = "extension '%s' is not registered"
                raise ValueError(msg % ext_id)
            del self._extensions[ext_id]
            grouped[extension.point].add(extension)

        for point_id, exts in grouped.iteritems():
            self._contributions[point_id].difference_update(exts)
            if point_id in self._extension_points:
                point = self._extension_points[point_id]
                self._update_extension_point(point, exts, ())
Remove extensions from a workbench.
dataset/ETHPy150Open nucleic/enaml/enaml/workbench/workbench.py/Workbench._remove_extensions