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