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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 src_file(self):
 """ Get the latest src_uri for a stage 3 tarball. Returns (str):
 Latest src_uri from gentoo's distfiles mirror. """

        try:
            src_uri = (curl[Gentoo._LATEST_TXT] | tail["-n", "+3"]
                       | cut["-f1", "-d "])().strip()
        except ProcessExecutionError as proc_ex:
            src_uri = "NOT-FOUND"
            LOG.error("Could not determine latest stage3 src uri: %s",
                      str(proc_ex))
        return src_uri