def get_verify_command(self, signature_filename, data_filename,<EOL>keystore=None):
cmd = [self.gpg, '<STR_LIT>', '<STR_LIT:2>', '<STR_LIT>']<EOL>if keystore is None:<EOL><INDENT>keystore = self.gpg_home<EOL><DEDENT>if keystore:<EOL><INDENT>cmd.extend(['<STR_LIT>', keystore])<EOL><DEDENT>cmd.extend(['<STR_LIT>', signature_filename, data_filename])<EOL>logger.debug('<STR_LIT>', '<STR_LIT:U+0020>'.join(cmd))<EOL>return cmd<EOL>
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`.