fn contains(&self, other: &Site) -> bool {
        if self.site.len() > other.site.len() {
            return false;
        }
        self.site.iter().zip(other.site.iter()).all(|(a, b)| a == b)
    }
Returns whether this site contains `other`.

A site contains `a` contains another site `b` if `a` is a prefix of `b`.

Returns `true` if the two sites are equal.
weld/src/optimizer/transforms/cse.rs