Function formulas_isomorphic 

pub fn formulas_isomorphic(
    num_vars: usize,
    f: &[Vec<Lit>],
    g: &[Vec<Lit>],
) -> Option<bool>

Whether two formulas over the same variables are isomorphic — equal up to a variable permutation preserving the (signed) clause structure — by comparing their canonical forms. None if either canonical form exceeds the search budget.