from my understanding, the `check_repeated_memory_variable` validator will raise an error if any of the variables in the `memories` list are repeated. However, the `load_memory_variables` method does not check for repeated variables. This means that it is possible for the `CombinedMemory` instance to return a dictionary of memory variables that contains duplicate values. This code will check for repeated variables in the `data` dictionary returned by the `load_memory_variables` method of each sub-memory. If a repeated variable is found, an error will be raised.