code: def isatty_to_env(cls, stdin, stdout, stderr):
      
      def gen_env_vars():
        for fd_id, fd in zip(STDIO_DESCRIPTORS, (stdin, stdout, stderr)):
          is_atty = fd.isatty()
          yield (cls.TTY_ENV_TMPL.format(fd_id), cls.encode_env_var_value(int(is_atty)))
          if is_atty:
            yield (cls.TTY_PATH_ENV.format(fd_id), os.ttyname(fd.fileno()) or b'')
      return dict(gen_env_vars())
docs: Generate nailgun tty capability environment variables based on checking a set of fds.
  
      :param file stdin: The stream to check for stdin tty capabilities.
      :param file stdout: The stream to check for stdout tty capabilities.
      :param file stderr: The stream to check for stderr tty capabilities.
      :returns: A dict containing the tty capability environment variables.