@classmethod
def get_by_address(cls, context, address):
    """Find portgroup by address and return a :class:`Portgroup` object.

        :param cls: the :class:`Portgroup`
        :param context: Security context
        :param address: The MAC address of a portgroup.
        :returns: A :class:`Portgroup` object.
        :raises: PortgroupNotFound

        """
    db_portgroup = cls.dbapi.get_portgroup_by_address(address)
    portgroup = cls._from_db_object(context, cls(), db_portgroup)
    return portgroup
