# File lib/kramdown/converter/base.rb, line 142
      def generate_id(str)
        gen_id = str.gsub(/^[^a-zA-Z]+/, '')
        gen_id.tr!('^a-zA-Z0-9 -', '')
        gen_id.tr!(' ', '-')
        gen_id.downcase!
        gen_id = 'section' if gen_id.length == 0
        @used_ids ||= {}
        if @used_ids.has_key?(gen_id)
          gen_id += '-' << (@used_ids[gen_id] += 1).to_s
        else
          @used_ids[gen_id] = 0
        end
        @options[:auto_id_prefix] + gen_id
      end