code: def hms_string(secs):
      
      l = hms(secs)
  
      def extend10(n):
          if n < 10:
              return '0' + str(n)
          else:
              return str(n)
  
      return extend10(l[0]) + ':' + extend10(l[1]) + ':' + extend10(l[2])
docs: return hours,minutes and seconds string, e.g. 02:00:45