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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 verify_file(self, file, sig_file=None):
 """Verify the signature on the contents of a file or file-like object. Can handle embedded signatures as well as detached signatures. If using detached signatures, the file containing the detached signature should be specified as the ``sig_file``. :param file file: A file descriptor object. :param str sig_file: A file containing the GPG signature data for ``file``. If given, ``file`` is verified via this detached signature. Its type will be checked with :func:`_util._is_file`. """


        result = self._result_map['verify'](self)

        if sig_file is None:
            log.debug("verify_file(): Handling embedded signature")
            args = ["--verify"]
            proc = self._open_subprocess(args)
            writer = _util._threaded_copy_data(file, proc.stdin)
            self._collect_output(proc, result, writer, stdin=proc.stdin)
        else:
            if not _util._is_file(sig_file):
                log.debug("verify_file(): '%r' is not a file" % sig_file)
                return result
            log.debug('verify_file(): Handling detached verification')
            sig_fh = None
            try:
                sig_fh = open(sig_file, 'rb')
                args = ["--verify %s -" % sig_fh.name]
                proc = self._open_subprocess(args)
                writer = _util._threaded_copy_data(file, proc.stdin)
                self._collect_output(proc, result, writer, stdin=proc.stdin)
            finally:
                if sig_fh and not sig_fh.closed:
                    sig_fh.close()
        return result