def _event_on_first_init(manager, cls):
 instrumenting_mapper = manager.info.get(_INSTRUMENTOR)
 if instrumenting_mapper:
  if Mapper._new_mappers:
   configure_mappers()

def _event_on_first_init ( manager , cls ) : instrumenting_mapper = manager . info . get ( _INSTRUMENTOR ) if instrumenting_mapper : if Mapper . _new_mappers : configure_mappers ( )
initial mapper compilation trigger .