docs: def _register_extensions(self, namespace):
          """Register any extensions under the given namespace."""
  
          # Register any extension classes for this class.
          extmanager = ExtensionManager(
              'extensions.classes.{}'.format(namespace),
              propagate_map_exceptions=True
          )
  
          if extmanager.extensions:
              extmanager.map(util.register_extension_class, base=self)
  
          # Register any extension methods for this class.
          extmanager = ExtensionManager(
              'extensions.methods.{}'.format(namespace),
              propagate_map_exceptions=True
          )
          if extmanager.extensions:
              extmanager.map(util.register_extension_method, base=self)