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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 exists(self, obj_id, obj_type=None):
 """ Return whether the given object exists in the search index. :param obj_id: The object's unique identifier. :param obj_type: The object's type. """

        return self.object_key(obj_id, obj_type) in self._data