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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 get_values(self, attr_name):
 """ Retrieves the unique set of values seen for the given attribute at this node. """

        ret = list(self._attr_value_cdist[attr_name].keys()) \
            + list(self._attr_value_counts[attr_name].keys()) \
            + list(self._branches.keys())
        ret = set(ret)
        return ret