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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 available_string(self, episode):
 """Return a string of available episodes."""

        available = [ep for ep in self if ep > episode]
        string = ','.join(str(ep) for ep in available[:self.EPISODES_TO_SHOW])
        if len(available) > self.EPISODES_TO_SHOW:
            string += '...'
        return string