def __setitem__(self, key, val):
        """Interpret ``val`` as a mapping of edges that end at ``dest``"""
        created = key not in self
        if key not in self._cache:
            self._cache[key] = self.Predecessors(self, key)
        preds = self._cache[key]
        preds.clear()
        preds.update(val)
        if created:
            self.send(self, key=key, val=val)
def __setitem__ ( self , key , val ) : created = key not in self if key not in self . _cache : self . _cache [ key ] = self . Predecessors ( self , key ) preds = self . _cache [ key ] preds . clear ( ) preds . update ( val ) if created : self . send ( self , key = key , val = val )
Interpret ``val`` as a mapping of edges that end at ``dest``