'Return an Issuer instance'

def _issuer(self, entityid=None):

    if entityid:
        if isinstance(entityid, Issuer):
            return entityid
        else:
            return Issuer(text=entityid, format=NAMEID_FORMAT_ENTITY)
    else:
        return Issuer(text=self.config.entityid, format=NAMEID_FORMAT_ENTITY)
