@ancestor.setter
    def ancestor(self, value):
        if not isinstance(value, Key):
            raise TypeError("Ancestor must be a Key")
        self._ancestor = value
**SUMMARY**
dataset/ETHPy150Open GoogleCloudPlatform/gcloud-python/gcloud/datastore/query.py/Query.ancestor--crossover with--dataset/ETHPy150Open sightmachine/SimpleCV/SimpleCV/Tracking/TrackSet.py/TrackSet.trackLength