code: def decrypt_file(self, filename, always_trust=False, passphrase=None,
                       output=None):
          
          args = ["--decrypt"]
          if output:  # write the output to a file with the specified name
              if os.path.exists(output):
                  os.remove(output) # to avoid overwrite confirmation message
              args.append('--output %s' % output)
          if always_trust:
              args.append("--always-trust")
          result = self._result_map['crypt'](self)
          self._handle_io(args, filename, result, passphrase, binary=True)
          log.debug('decrypt result: %r', result.data)
          return result
docs: Decrypt the contents of a file-like object ``filename`` .
  
          :param str filename: A file-like object to decrypt.
          :param bool always_trust: Instruct GnuPG to ignore trust checks.
          :param str passphrase: The passphrase for the secret key used for decryption.
          :param str output: A filename to write the decrypted output to.