def comments_of_file(file)
      File.readlines(file).map { |s| s[2..-1].rstrip if s.start_with?('# ') }.compact
    end
def comments_of_file(file)
      File.readlines(file).map { |s| s[2..-1].rstrip if s.start_with?('# ') }.compact
    end
Fetch lines start with '#'.
 @param [String] file
   Filename.
 @return [Array<String>]
   Lines of comments.