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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 attribute_crawl(self, key):
 """ Grab all attribute values associated with the given feature. Traverse the given feature (and all of its descendants) to find all values associated with the given attribute key. ['Ot01g00060', 'XM_003074019.1', 'XP_003074065.1'] ['Ot01g00070', 'XM_003074020.1', 'XP_003074066.1'] ['Ot01g00080', 'XM_003074021.1', 'XP_003074067.1'] ['Ot01g00090', 'XM_003074022.1', 'XP_003074068.1'] ['Ot01g00100', 'XM_003074023.1', 'XP_003074069.1'] ['Ot01g00110', 'XM_003074024.1', 'XP_003074070.1'] """

        union = set()
        for feature in self:
            values = feature.get_attribute(key, as_list=True)
            if values is not None:
                union.update(set(values))
        return union