Go through the sequence of zone files discovered in a block range, and reindex the names' subdomains.

def index_blockchain(self, block_start, block_end):
        """
        Go through the sequence of zone files discovered in a block range, and reindex the names' subdomains.
        """
        log.debug("Processing subdomain updates for zonefiles in blocks {}-{}".format(block_start, block_end))
        
        res = self.find_zonefile_subdomains(block_start, block_end)
        zonefile_subdomain_info = res['zonefile_info']

        self.process_subdomains(zonefile_subdomain_info)