[Django]-Authenticate() is not running with custom authentication backend

The method should look like :

def authenticate(self, request, username=None, password=None):

You can can check the parameters needed for the signature of the method authenticate by looking at the source of authentication system. The first positioned parameter is request, and then the credentials are unpacked as named parameters:

def authenticate(request=None, **credentials):
    """
    If the given credentials are valid, return a User object.
    """
    for backend, backend_path in _get_backends(return_tuples=True):
        try:
            inspect.getcallargs(backend.authenticate, request, **credentials)
        except TypeError:
            # This backend doesn't accept these credentials as arguments. Try the next one.
            continue
        try:
            user = backend.authenticate(request, **credentials)
     [...]

(_get_backends represents the list of all backends in settings.AUTHENTICATION_BACKENDS)

Doc about custom authentication :
https://docs.djangoproject.com/en/dev/topics/auth/customizing/#writing-an-authentication-backend