docs: def str_val(val):
      """
      Format the value of a metric value to a string
  
      :param val: number to be formatted
      :return: a string with the formatted value
      """
      str_val = val
      if val is None:
          str_val = "NA"
      elif type(val) == float:
          str_val = '%0.2f' % val
      else:
          str_val = str(val)
      return str_val