in src/builder.rs [229:238]
fn insert(&mut self, item: T) -> bool {
let mut eq = item.as_query(self.m);
eq.b = if item.included() { 0 } else { 1 };
assert!(eq.is_zero() || eq.a[0] & 1 == 1);
let rv = self.insert_equation(eq);
if !rv {
self.exceptions.push(item)
}
rv
}