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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 _file_path(self, container: Container, fn: str) -> str: """ Computes the base path for a given file. """

        fn = self.resolve(container, fn)
        assert fn[0] == '/'
        fn = fn[1:]
        path = "files/{}/{}".format(container.uid, fn)
        return path