# File lib/backports/2.5.0/string/delete_suffix.rb, line 21
    def delete_suffix!(suffix)
      suffix = Backports.coerce_to_str(suffix)
      chomp! if frozen?
      len = suffix.length
      if len > 0 && index(suffix, -len)
        self[-len..-1] = ''
        self
      else
        nil
      end
    end