'Check protection for list assignment for tree API.
The policy rule might want to inspect the domain of any project filter
so if one is defined, then load the project ref and pass it to the
check protection method.'

def _check_list_tree_protection(self, request, protection_info):

    ref = {}
    for (filter, value) in protection_info.get('filter_attr', {}).items():
        if ((filter == 'scope.project.id') and value):
            ref['project'] = self.resource_api.get_project(value)
    self.check_protection(request, protection_info, ref)
