'Sync the chunk cache to storage.'

def Flush(self, sync=True):

    if self._dirty:
        self.Set(self.Schema.SIZE(self.size))
        if (self.content_last is not None):
            self.Set(self.Schema.CONTENT_LAST, self.content_last)
    self.chunk_cache.Flush()
    super(AFF4ImageBase, self).Flush(sync=sync)
