@property
    def boundary(self):
        return self._boundary
Called when we start a new resumable upload or get a new tracker
dataset/ETHPy150Open sympy/sympy/sympy/sets/sets.py/Set.boundary--crossover with--dataset/ETHPy150Open radlab/sparrow/deploy/third_party/boto-2.1.1/boto/gs/resumable_upload_handler.py/ResumableUploadHandler._set_tracker_uri