code: def on_commit(self, changes):
          
          if _get_config(self)['enable_indexing'] is False:
              return None
  
          for wh in self.whoosheers:
              if not wh.auto_update:
                  continue
              writer = None
              for change in changes:
                  if change[0].__class__ in wh.models:
                      method_name = '{0}_{1}'.format(change[1], change[0].__class__.__name__.lower())
                      method = getattr(wh, method_name, None)
                      if method:
                          if not writer:
                              writer = type(self).get_or_create_index(_get_app(self), wh).\
                                  writer(timeout=_get_config(self)['writer_timeout'])
                          method(writer, change[0])
              if writer:
                  writer.commit()
docs: Method that gets called when a model is changed. This serves
          to do the actual index writing.