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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 list_classes(mod_name):
 """Lists all classes declared in a module. Args: mod_name: the module name Returns: A list of functions declared in that module. """

    mod = sys.modules[mod_name]
    return [cls.__name__ for cls in mod.__dict__.values()
            if is_mod_class(mod, cls)]