code: def _group(self, value: str):
          
          reversed_v = value[::-1]
  
          parts = []
  
          has_period = False
          for c in reversed_v:
              if has_period:
                  parts.append(c + '.')
                  has_period = False
              elif c == '.':
                  has_period = True
              else:
                  parts.append(c)
  
          parts = parts[:len(self._digits)]
  
          return parts
docs: Takes a string and groups it appropriately with any
          period or other appropriate punctuation so that it is
          displayed correctly.
          :param value: a string containing an integer or float
          :return: None