def each_line
      original_line_number = @original_line_number
      modified_line_number = @modified_line_number

      @lines.each do |line|
        if line.addition?
          yield line, nil, modified_line_number
          modified_line_number += 1
        elsif line.deletion?
          yield line, original_line_number, nil
          original_line_number += 1
        elsif line.unchanged?
          yield line, original_line_number, modified_line_number
          original_line_number += 1
          modified_line_number += 1
        else
          yield line
        end
      end
    end
def each_line
      original_line_number = @original_line_number
      modified_line_number = @modified_line_number

      @lines.each do |line|
        if line.addition?
          yield line, nil, modified_line_number
          modified_line_number += 1
        elsif line.deletion?
          yield line, original_line_number, nil
          original_line_number += 1
        elsif line.unchanged?
          yield line, original_line_number, modified_line_number
          original_line_number += 1
          modified_line_number += 1
        else
          yield line
        end
      end
    end
Iterator for lines passing |line, original_line_number, modified_line_number| as block arguments