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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def threadsafe_call(self, fn, *args, **kwargs):
 """Wrapper around `AsyncSession.threadsafe_call`."""

        def handler():
            try:
                fn(*args, **kwargs)
            except Exception:
                warn("error caught while excecuting async callback\n%s\n",
                     format_exc())

        def greenlet_wrapper():
            gr = greenlet.greenlet(handler)
            gr.switch()

        self._async_session.threadsafe_call(greenlet_wrapper)