Function reduce_32 

pub fn reduce_32<C: Config>(
    builder: &mut Builder<C>,
    vals: &[Felt<C::F>],
) -> Var<C::N>

Reference: https://github.com/Plonky3/Plonky3/blob/622375885320ac6bf3c338001760ed8f2230e3cb/field/src/helpers.rs#L136