How to use the blinker._saferef.safe_ref function in blinker

def test_ShortCircuit(self):
        """Test that creation short-circuits to reuse existing references"""
        sd = {}
        for s in self.ss:
            sd[s] = 1
        for t in self.ts:
            if hasattr(t, 'x'):
                assert safe_ref(t.x) in sd
            else:
                assert safe_ref(t) in sd

def test_ShortCircuit(self):
        """Test that creation short-circuits to reuse existing references"""
        sd = {}
        for s in self.ss:
            sd[s] = 1
        for t in self.ts:
            if hasattr(t, 'x'):
                assert safe_ref(t.x) in sd
            else:
                assert safe_ref(t) in sd

def test_In(self):
        """Test the `in` operator for safe references (cmp)"""
        for t in self.ts[:50]:
            assert safe_ref(t.x) in self.ss

def setUp(self):
        ts = []
        ss = []
        for x in range(100):
            t = _Sample1()
            ts.append(t)
            s = safe_ref(t.x, self._closure)
            ss.append(s)
        ts.append(_sample2)
        ss.append(safe_ref(_sample2, self._closure))
        for x in range(30):
            t = _Sample3()
            ts.append(t)
            s = safe_ref(t, self._closure)
            ss.append(s)
        self.ts = ts
        self.ss = ss
        self.closure_count = 0

def setUp(self):
        ts = []
        ss = []
        for x in range(100):
            t = _Sample1()
            ts.append(t)
            s = safe_ref(t.x, self._closure)
            ss.append(s)
        ts.append(_sample2)
        ss.append(safe_ref(_sample2, self._closure))
        for x in range(30):
            t = _Sample3()
            ts.append(t)
            s = safe_ref(t, self._closure)
            ss.append(s)
        self.ts = ts
        self.ss = ss
        self.closure_count = 0

def setUp(self):
        ts = []
        ss = []
        for x in range(100):
            t = _Sample1()
            ts.append(t)
            s = safe_ref(t.x, self._closure)
            ss.append(s)
        ts.append(_sample2)
        ss.append(safe_ref(_sample2, self._closure))
        for x in range(30):
            t = _Sample3()
            ts.append(t)
            s = safe_ref(t, self._closure)
            ss.append(s)
        self.ts = ts
        self.ss = ss
        self.closure_count = 0

def subscribe(self, func, opts):
        """
            Subscribe a callable to the .changed signal, but only for a
            specified list of options. The callable should accept arguments
            (options, updated), and may raise an OptionsError.

            The event will automatically be unsubscribed if the callable goes out of scope.
        """
        for i in opts:
            if i not in self._options:
                raise exceptions.OptionsError("No such option: %s" % i)

        # We reuse blinker's safe reference functionality to cope with weakrefs
        # to bound methods.
        func = blinker._saferef.safe_ref(func)

        @functools.wraps(func)
        def _call(options, updated):
            if updated.intersection(set(opts)):
                f = func()
                if f:
                    f(options, updated)
                else:
                    self.changed.disconnect(_call)

        # Our wrapper function goes out of scope immediately, so we have to set
        # weakrefs to false. This means we need to keep our own weakref, and
        # clean up the hook when it's gone.
        self.changed.connect(_call, weak=False)