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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 get_verify_command(self, signature_filename, data_filename, keystore=None):
 """ Return a suitable command for verifying a file. :param signature_filename: The pathname to the file containing the signature. :param data_filename: The pathname to the file containing the signed data. :param keystore: The path to a directory which contains the keys used in verification. If not specified, the instance's ``gpg_home`` attribute is used instead. :return: The verifying command as a list suitable to be passed to :class:`subprocess.Popen`. """

        cmd = [self.gpg, '--status-fd', '2', '--no-tty']
        if keystore is None:
            keystore = self.gpg_home
        if keystore:
            cmd.extend(['--homedir', keystore])
        cmd.extend(['--verify', signature_filename, data_filename])
        logger.debug('invoking: %s', ' '.join(cmd))
        return cmd