code: def rollback             (self, n=None):
  		
  		
  		if n is None:
  			if self.haveSnapshots: return self.fromSnapshot(self.latestLink)
  			else:                  return self.fromScratch()
  		elif isinstance(n, int):
  			loadSnapshotPath = self.getFullPathToSnapshot(n)
  			assert(os.path.isdir(loadSnapshotPath))
  			return self.__markLatest(n).fromSnapshot(loadSnapshotPath)
  		else:
  			raise ValueError("n must be int, or None!")
docs: Roll back the experiment to the given snapshot number.
  		
  		Returns `self`.