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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 GetUnknownFiles(self):
 		"""Return a list of files unknown to the VCS."""

		args = []
		status = RunShell(["hg", "status", "--rev", self.base_rev, "-u", "."],
				silent_ok=True)
		unknown_files = []
		for line in status.splitlines():
			st, fn = line.split(" ", 1)
			if st == "?":
				unknown_files.append(fn)
		return unknown_files