<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def create_prefetch(self, addresses):
 """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). """


        with self._lock:
            for add in addresses:
                self._state[add] = _ContextFuture(address=add,
                                                  wait_for_tree=True)