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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 _switch(self, future):
 """Switch greenlet."""

        scoop._control.current = self
        assert self.greenlet is not None, ("No greenlet to switch to:"
                                           "\n{0}".format(self.__dict__))
        return self.greenlet.switch(future)