# File lib/sass/error.rb, line 106
    def modify_backtrace(attrs)
      attrs = attrs.reject {|k, v| v.nil?}
      # Move backwards through the backtrace
      (0...sass_backtrace.size).to_a.reverse.each do |i|
        entry = sass_backtrace[i]
        sass_backtrace[i] = attrs.merge(entry)
        attrs.reject! {|k, v| entry.include?(k)}
        break if attrs.empty?
      end
    end