docs: def _save_group_field(self, field_type, group):
          """This method packs a group field"""
          
          if field_type == 0x0000:
              # Ignored (commentar block)
              pass
          elif field_type == 0x0001:
              if group.id_ is not None:
                  return (4, struct.pack('<I', group.id_))
          elif field_type == 0x0002:
              if group.title is not None:
                  return (len(group.title.encode())+1,
                          (group.title+'\0').encode())
          elif field_type == 0x0003:
              if group.creation is not None:
                  return (5, self._pack_date(group.creation))
          elif field_type == 0x0004:
              if group.last_mod is not None:
                  return (5, self._pack_date(group.last_mod))
          elif field_type == 0x0005:
              if group.last_access is not None:
                  return (5, self._pack_date(group.last_access))
          elif field_type == 0x0006:
              if group.expire is not None:
                  return (5, self._pack_date(group.expire))
          elif field_type == 0x0007:
              if group.image is not None:
                  return (4, struct.pack('<I', group.image))
          elif field_type == 0x0008:
              if group.level is not None:
                  return (2, struct.pack('<H', group.level))
          elif field_type == 0x0009:
              if group.flags is not None:
                  return (4, struct.pack('<I', group.flags))
          return False