code: def str_banner(txt=None, c="#", debug=True):
      
      line = ""
      if debug:
          line += "\n"
          line += "# " + str(70 * c)
          if txt is not None:
              line += "# " + txt
              line += "# " + str(70 * c)
      return line
docs: prints a banner of the form with a frame of # around the txt::
  
        ############################
        # txt
        ############################
  
      :param debug: return "" if not in debug
      :type debug: boolean
      :param txt: a text message to be printed
      :type txt: string
      :param c: the character used instead of c
      :type c: character