code: def create_prefetch(self, addresses):
          
  
          with self._lock:
              for add in addresses:
                  self._state[add] = _ContextFuture(address=add,
                                                    wait_for_tree=True)
docs: Create futures needed before starting the process of reading the
          address's value from the merkle tree.
  
          Args:
              addresses (list of str): addresses in the txn's inputs that
                  aren't in any base context (or any in the chain).