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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 availability(self):
 """ Retrieves the availability of the entity pointed at by the cursor. """

        if not hasattr(self, '_availability'):
            self._availability = conf.lib.clang_getCursorAvailability(self)

        return AvailabilityKind.from_id(self._availability)