def METHOD_NAME(self):
    """Updates cached overview"""
    overview = self.protocol.map.get_overview(rgba=True)
    image = Image.frombytes('RGBA', (512, 512), overview)
    data = BytesIO()
    image.save(data, 'png')
    self.cached_overview = data.getvalue()
    self.last_update = time.time()
    self.last_map_name = self.protocol.map_info.name