def test_nestedDeprecation(self):
        """
        L{callDeprecated} ignores all deprecations apart from the first.

        Multiple warnings are generated when a deprecated function calls
        another deprecated function. The first warning is the one generated by
        the explicitly called function. That's the warning that we care about.
        """
        differentVersion = Version('Foo', 1, 2, 3)

        def nestedDeprecation(*args):
            return oldMethod(*args)
        nestedDeprecation = deprecated(differentVersion)(nestedDeprecation)

        self.callDeprecated(differentVersion, nestedDeprecation, 24)

        # The oldMethod deprecation should have been emitted too, not captured
        # by callDeprecated.  Flush it now to make sure it did happen and to
        # prevent it from showing up on stdout.
        warningsShown = self.flushWarnings()
        self.assertEqual(len(warningsShown), 1,
            "Unexpected warnings: {}".format(warningsShown))

        L{callDeprecated} ignores all deprecations apart from the first.

        Multiple warnings are generated when a deprecated function calls
        another deprecated function. The first warning is the one generated by
        the explicitly called function. That's the warning that we care about.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_assertions.py