code: def GroupSizer(field_number, is_repeated, is_packed):
    
  
    tag_size = _TagSize(field_number) * 2
    assert not is_packed
    if is_repeated:
      def RepeatedFieldSize(value):
        result = tag_size * len(value)
        for element in value:
          result += element.ByteSize()
        return result
      return RepeatedFieldSize
    else:
      def FieldSize(value):
        return tag_size + value.ByteSize()
      return FieldSize
docs: Returns a sizer for a group field.