How to insert a simple "rit."?

[Kenneth Wolcott]

Hi;

  Looks like I must be missing something obvious in the lilypond docs
(2.20.2)...

  How to insert a "rit."?

I saw the following in the "Hiding the extender line for text dynamics" snippet.

\relative c'' {
  \override DynamicTextSpanner.style = #'none
  \crescTextCresc
  c1\< | d | b | c\!
}

Obviously snippet pertains to dynamics; is there something similar for
tempo adjustments?

Thanks,
Ken Wolcott