code: def is_subdomain_zonefile_hash(fqn, zonefile_hash, db_path=None, zonefiles_dir=None):
      
      opts = get_blockstack_opts()
      if not is_subdomains_enabled(opts):
          return []
  
      if db_path is None:
          db_path = opts['subdomaindb_path']
      
      if zonefiles_dir is None:
          zonefiles_dir = opts['zonefiles']
  
      db = SubdomainDB(db_path, zonefiles_dir)
      zonefile_hashes = db.is_subdomain_zonefile_hash(fqn, zonefile_hash)
      return zonefile_hashes
docs: Static method for getting all historic zone file hashes for a subdomain