def ChunksExist(self, chunk_numbers):
    """Do we have this chunk in the index?"""
    index_urns = {
        self.urn.Add(self.CHUNK_ID_TEMPLATE % chunk_number): chunk_number
        for chunk_number in chunk_numbers
    }

    res = {chunk_number: False for chunk_number in chunk_numbers}

    for metadata in aff4.FACTORY.Stat(index_urns):
      res[index_urns[metadata["urn"]]] = True

    return res
Do we have this chunk in the index?