code: def get_subdomain_DID_info(fqn, db_path=None, zonefiles_dir=None):
      
      opts = get_blockstack_opts()
      if not is_subdomains_enabled(opts):
          log.warn("Subdomain support is disabled")
          return None
  
      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)
      try:
          subrec = db.get_subdomain_entry(fqn)
      except SubdomainNotFound:
          log.warn("No such subdomain: {}".format(fqn))
          return None
      
      try:
          return db.get_subdomain_DID_info(fqn)
      except SubdomainNotFound:
          return None
docs: Get a subdomain's DID info.
      Return None if not found