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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 current() -> 'Process': """ Returns the instance of the process that is executing at the current moment. """

        curr = greenlet.getcurrent()
        if not isinstance(curr, Process):
            raise TypeError("Current greenlet does not correspond to a Process instance.")
        return cast(Process, greenlet.getcurrent())