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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 overlays_at(self, key):
 """ Key may be a slice or a point. """


        if isinstance(key, slice):
            s, e, _ = key.indices(len(self.text))
        else:
            s = e = key

        return [o for o in self.overlays if o.start in Rng(s, e)]