code: def handle_format_group(self, field, text):
          
  
          # Handle auto incrementing group indexes
          if field == '':
              if self.auto:
                  field = str(self.auto_index)
                  text[0] = (_util.FMT_FIELD, field)
                  self.auto_index += 1
              elif not self.manual and not self.auto:
                  self.auto = True
                  field = str(self.auto_index)
                  text[0] = (_util.FMT_FIELD, field)
                  self.auto_index += 1
              else:
                  raise ValueError("Cannot switch to auto format during manual format!")
          elif not self.manual and not self.auto:
              self.manual = True
          elif not self.manual:
              raise ValueError("Cannot switch to manual format during auto format!")
  
          self.handle_group(field, tuple(text), True)
docs: Handle format group.