# File lib/rd/rd2man-lib.rb, line 175
    def apply_to_Index(element, content)
      tmp = []
      element.each do |i|
        tmp.push(i) if i.is_a?(String)
      end
      key = meta_char_escape(tmp.join)
      if @index.has_key?(key)
        # warning?
        ""
      else
        num = @index[key] = @index.size
        %{\\&\\fB#{content.join.sub(/\./, '\\.')}\\fP}
      end
    end