'Create a new assignment/grant.
If the assignment is to a domain, then optionally it may be
specified as inherited to owned projects (this requires
the OS-INHERIT extension to be enabled).'

@abc.abstractmethod
def create_grant(self, role_id, user_id=None, group_id=None, domain_id=None, project_id=None, inherited_to_projects=False):

    raise exception.NotImplemented()
