fn find_novel_lines(
lines: &[(Option<LineNumber>, Option<LineNumber>)],
all_lhs_novel: &FxHashSet<LineNumber>,
all_rhs_novel: &FxHashSet<LineNumber>,
) -> (FxHashSet<LineNumber>, FxHashSet<LineNumber>)fn find_novel_lines(
lines: &[(Option<LineNumber>, Option<LineNumber>)],
all_lhs_novel: &FxHashSet<LineNumber>,
all_rhs_novel: &FxHashSet<LineNumber>,
) -> (FxHashSet<LineNumber>, FxHashSet<LineNumber>)