docs: def open_fd(cls, name):
          """Open a file or create it."""
          # Try to create it, if can't, try to open.
          try:
              return os.open(name, os.O_CREAT | os.O_RDWR | os.O_EXCL)
          except OSError as e:
              if e.errno != errno.EEXIST:
                  raise
              return os.open(name, os.O_RDWR | os.O_EXCL)