pub(crate) fn rewrite_pair<LHS, RHS>(
    lhs: &LHS,
    rhs: &RHS,
    pp: PairParts<'_>,
    context: &RewriteContext<'_>,
    shape: Shape,
    separator_place: SeparatorPlace
) -> Option<String>where
    LHS: Rewrite,
    RHS: Rewrite,