code: def get_if_not_set(self, addresses):
          
  
          with self._lock:
              results = []
              for add in addresses:
                  results.append(self._get_if_not_set(add))
              return results
docs: Returns the value at an address if it was an input to the txn but
          never set. It returns None if that address was never set in the
          merkle database, or if the address is not within the context.
  
          Args:
              addresses (list of str): The full 70 character addresses.
  
          Returns:
              (list): bytes at that address but not set within the context