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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 _checkout(self):
 """ check out the image filesystem on self.mount_point """

        cmd = ["atomic", "mount", "--storage", "ostree", self.ref_image_name, self.mount_point]
        # self.mount_point has to be created by us
        self._run_and_log(cmd, self.ostree_path,
                          "Failed to mount selected image as an ostree repo.")