Function variable_automorphism_generators 

pub fn variable_automorphism_generators(
    num_vars: usize,
    clauses: &[Vec<Lit>],
) -> Option<Vec<Perm>>

The variable-permutation automorphism GENERATORS of a CNF (phase-free symmetries), without enumerating the group — fast, no size cap. None if a detected symmetry flips a phase (a value symmetry this variable scheme does not cover). An empty vector means no non-trivial symmetry.