Function lemma_and_then_prepare_congruence 

pub broadcast proof fn lemma_and_then_prepare_congruence<A1, A2, B1, B2>(
    a: AndThen<A1, B1>,
    b: AndThen<A2, B2>,
)
where
    A1: BytesCombinator + Consistency<Val = Seq<u8>>,
    A2: BytesCombinator + Consistency<Val = Seq<u8>>,
    B1: Consistency + SpecByteLen<T = B1::Val>,
    B2: Consistency<Val = B1::Val> + SpecByteLen<T = B1::Val>,

requires

prepare_congruent(a.0, b.0),

prepare_congruent(a.1, b.1),

ensures

#[trigger] prepare_congruent(a, b),