code: def _subclass(self, parser):
          '''
          Create sub-classed struct from extra data, with specified parser. For parser internal use.
          
          :param parser: parser of subclass 
          '''
          _set(self, '_sub', parser._create(memoryview(getattr(self, '_extra', b'')), self._target))
          try:
              object.__delattr__(self, '_extra')
          except:
              pasf _subclass(self, parser):
          '''
          Create sub-classed struct from extra data, with specified parser. For parser internal use.
          
          :param parser: parser of subclass 
          '''
          _set(self, '_sub', parser._create(memoryview(getattr(self, '_extra', b'')), self._target))
          try:
              object.__delattr__(self, '_extra')
          except:
              pass
docs: Create sub-classed struct from extra data, with specified parser. For parser internal use.
          
          :param parser: parser of subclass