'Do we have this chunk in the index?'

def ChunksExist(self, chunk_numbers):

    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, token=self.token):
        res[index_urns[metadata['urn']]] = True
    return res
