pm.Truncated can handle Truncation from below and/or above. For instance if you can’t observe values below 1 or above 4 you can set lower=1, upper=4.
Truncation in the middle (e.g., values between 1 and 4 can’t be observed) is not supported. You can define this density manually with pm.Potential, you basically have to rescale the untruncated density by 1-(dist.cdf(4) - dist.cdf(1). I can help you through that if that’s indeed your case.