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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 get_class_from_settings(settings_key):
 """Gets a class from a setting key. This will first check loaded models, then look in installed apps, then fallback to import from lib. :param settings_key: the key defined in settings to the value for """

    cls_path = getattr(settings, settings_key, None)
    if not cls_path:
        raise NotImplementedError()

    try:
        # First check to see if it's an installed model
        return get_model_from_settings(settings_key=settings_key)
    except:
        try:
            # Next, check from installed apps
            return get_class_from_settings_from_apps(settings_key=settings_key)
        except:
            # Last, try to load from the full path
            return get_class_from_settings_full_path(settings_key)