code: def is_new_preorder( self, preorder_hash, lastblock=None ):
          
          if lastblock is None:
              lastblock = self.lastblock 
  
          preorder = namedb_get_name_preorder( self.db, preorder_hash, lastblock )
          if preorder is not None:
              return False
          else:
              return True
docs: Given a preorder hash of a name, determine whether or not it is unseen before.