An example of the creation of a full-fledged signal.

signal.py

from blinker import Namespace

_signals = Namespace()
pre_save = _signals.signal('pre_save')


class Sender:
    def __init__(self, name):
        self.name = name

    def caller(self):
        return pre_save.send(self, save=True)

    @classmethod
    def receiver(cls, sender, **kwargs):
        print(f'Sender is {sender}. Kwargs: {kwargs}.')
        return sender

    def __repr__(self):
        return f'<Sender {self.name}>'


s = Sender('testing')
pre_save.connect(Sender.receiver, sender=s)
print(pre_save.receivers)
s.caller()