def validate_id_is_docker_compatible(value):
 match = re.match(u'^[a-z0-9-]+$', value)
 if (not match):
  raise ValidationError(u'App IDs can only contain [a-z0-9-].')

def validate_id_is_docker_compatible ( value ) : match = re . match ( u'^[a-z0-9-]+$' , value ) if ( not match ) : raise ValidationError ( u'App IDs can only contain [a-z0-9-].' )
check that the id follows dockers image name constraints .