bulk creation does not work

It seems bulk creation does not work in API v2.0's plugin.
This is from base.py:
    def create(self, request, body=None):
        """Creates a new instance of the requested entity"""

        body = self._prepare_request_body(request.context, body, True,
                                          allow_bulk=True)

        action = "create_%s" % self._resource

        # Check authz
        try:
            if self._collection in body:
                # Have to account for bulk create
                for item in body[self._collection]:
                    self._validate_network_tenant_ownership(
                        request,
                        item[self._resource],
                    )
                    policy.enforce(
                        request.context,
                        action,
                        item[self._resource],
                    )
            else:
                self._validate_network_tenant_ownership(
                    request,
                    body[self._resource]
                )
                policy.enforce(request.context, action, body[self._resource])
        except exceptions.PolicyNotAuthorized:
            raise webob.exc.HTTPForbidden()

        obj_creator = getattr(self._plugin, action)
        kwargs = {self._resource: body}
        obj = obj_creator(request.context, **kwargs)
        return {self._resource: self._view(obj)}
This is creator for each resource in db_base_plugin_v2.py:
    def create_port(self, context, port):
        p = port['port']
    def create_subnet(self, context, subnet):
        s = subnet['subnet']
    def create_network(self, context, network):
        n = network['network']
I cannot see any of them can deal with bulk creation.