docs: def setns(fd, nstype):
      """
      Reassociate thread with a namespace
  
      :param fd int: The file descriptor referreing to one of the namespace
          entries in a :directory::`/proc/<pid>/ns/` directory.
      :param nstype int: The type of namespace the calling thread should be
          reasscoiated with.
      """
      res = lib.setns(fd, nstype)
      if res != 0:
          _check_error(ffi.errno)