How to use the blinker._utilities.WeakTypes function in blinker

def receivers_for(self, sender):
        """Iterate all live receivers listening for *sender*."""
        # TODO: test receivers_for(ANY)
        if self.receivers:
            sender_id = hashable_identity(sender)
            if sender_id in self._by_sender:
                ids = (self._by_sender[ANY_ID] |
                       self._by_sender[sender_id])
            else:
                ids = self._by_sender[ANY_ID].copy()
            for receiver_id in ids:
                receiver = self.receivers.get(receiver_id)
                if receiver is None:
                    continue
                if isinstance(receiver, WeakTypes):
                    strong = receiver()
                    if strong is None:
                        self._disconnect(receiver_id, ANY_ID)
                        continue
                    receiver = strong
                yield receiver

def receivers_for(self, sender):
        """Iterate all live receivers listening for *sender*."""
        # TODO: test receivers_for(ANY)
        if self.receivers:
            sender_id = hashable_identity(sender)
            if sender_id in self._by_sender:
                ids = (self._by_sender[ANY_ID] |
                       self._by_sender[sender_id])
            else:
                ids = self._by_sender[ANY_ID].copy()
            for receiver_id in ids:
                receiver = self.receivers.get(receiver_id)
                if receiver is None:
                    continue
                if isinstance(receiver, WeakTypes):
                    strong = receiver()
                    if strong is None:
                        self._disconnect(receiver_id, ANY_ID)
                        continue
                    receiver = strong
                yield receiver

def receivers_for(self, sender):
        """Iterate all live receivers listening for *sender*."""
        # TODO: test receivers_for(ANY)
        if self.receivers:
            sender_id = hashable_identity(sender)
            if sender_id in self._by_sender:
                ids = (self._by_sender[ANY_ID] |
                       self._by_sender[sender_id])
            else:
                ids = self._by_sender[ANY_ID].copy()
            for receiver_id in ids:
                receiver = self.receivers.get(receiver_id)
                if receiver is None:
                    continue
                if isinstance(receiver, WeakTypes):
                    strong = receiver()
                    if strong is None:
                        self._disconnect(receiver_id, ANY_ID)
                        continue
                    receiver = strong
                yield receiver

def receivers_for(self, sender):
        """Iterate all live receivers listening for *sender*."""
        # TODO: test receivers_for(ANY)
        if self.receivers:
            sender_id = hashable_identity(sender)
            if sender_id in self._by_sender:
                ids = (self._by_sender[ANY_ID] |
                       self._by_sender[sender_id])
            else:
                ids = self._by_sender[ANY_ID].copy()
            for receiver_id in ids:
                receiver = self.receivers.get(receiver_id)
                if receiver is None:
                    continue
                if isinstance(receiver, WeakTypes):
                    strong = receiver()
                    if strong is None:
                        self._disconnect(receiver_id, ANY_ID)
                        continue
                    receiver = strong
                yield receiver

def receivers_for(self, sender):
        """Iterate all live receivers listening for *sender*."""
        # TODO: test receivers_for(ANY)
        if self.receivers:
            sender_id = hashable_identity(sender)
            if sender_id in self._by_sender:
                ids = (self._by_sender[ANY_ID] |
                       self._by_sender[sender_id])
            else:
                ids = self._by_sender[ANY_ID].copy()
            for receiver_id in ids:
                receiver = self.receivers.get(receiver_id)
                if receiver is None:
                    continue
                if isinstance(receiver, WeakTypes):
                    strong = receiver()
                    if strong is None:
                        self._disconnect(receiver_id, ANY_ID)
                        continue
                    receiver = strong
                yield receiver