Function expand 

pub fn expand(
    conjuncts: &[Expr],
    arrays: &[ArrayState],
    sizes: &[usize],
    n_vars0: u32,
    states: &[Option<BigUint>],
) -> Result<Expanded, ExpandError>

Expands the array-level conjuncts for the array sizes sizes (module docs). n_vars0 is how many field variables the conjuncts already number; element variables are numbered after them. states are the caller’s state values (an element of an inactive array becomes a state appended after them).