This is a process unique Stdio.Fd that is used to receive remote file descriptors and arguments to Process.create_process , as well as signalling back status changes and errors.
inherit Stdio.Fd : Fd
array(Stdio.Fd) Tools.Standalone.forkd.ForkFd.fds
The remote file descriptors received so far in order.
Tools.Standalone.forkd()->FdStream