def METHOD_NAME(self, content: Union[bytes, memoryview]):
    if not self._initialized:
        self._write_init()
        self._initialized = True
    offset = self._offset
    content_length = getattr(content, "nbytes", len(content))
    new_offset = offset + content_length
    self._mv[offset:new_offset] = content
    self._offset = new_offset