code: def get_verify_command(self, signature_filename, data_filename,
                             keystore=None):
          
          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
docs: 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`.