code: def check_subdomain_transition(cls, existing_subrec, new_subrec):
          
          if existing_subrec.get_fqn() != new_subrec.get_fqn():
              return False
  
          if existing_subrec.n + 1 != new_subrec.n:
              return False
  
          if not new_subrec.verify_signature(existing_subrec.address):
              log.debug("Invalid signature from {}".format(existing_subrec.address))
              return False
  
          if virtualchain.address_reencode(existing_subrec.address) != virtualchain.address_reencode(new_subrec.address):
              if new_subrec.independent:
                  log.debug("Transfer is independent of domain: {}".format(new_subrec))
                  return False
  
          return True
docs: Given an existing subdomain record and a (newly-discovered) new subdomain record,
          determine if we can use the new subdomain record (i.e. is its signature valid? is it in the right sequence?)
          Return True if so
          Return False if not