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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def register_module_classes(yaml: ruamel.yaml.YAML, modules: Optional[Iterable[Any]] = None) -> ruamel.yaml.YAML: """ Register all classes in the given modules with the YAML object. This is a simple helper function. """

    # Validation
    if modules is None:
        modules = []

    # Extract the classes from the modules
    classes_to_register = set()
    for module in modules:
        module_classes = [member[1] for member in inspect.getmembers(module, inspect.isclass)]
        classes_to_register.update(module_classes)

    # Register the extracted classes
    return register_classes(yaml = yaml, classes = classes_to_register)