The opposite of ##f

[David Sumbler]

A steep learning curve, using Lilypond!  I've found answers in the
documentation to most of the problems, but after an hour of searching
I'm stumped on this one.

I used '\override TupletNumber #'stencil = ##f' earlier in my file.

Now I want to cancel that setting and restore tuplet numbers.

I have tried '\override TupletNumber #'stencil = ##t', which seemed the
obvious choice.  And, guess what, it works!  But it produces a warning
"value 't' must be of type 'unknown'", so it is clearly not the proper
way to do it.

What should I put instead?

David