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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_cat_model(model):
 """ Return a class from a string or class """

    try:
        if isinstance(model, string_types):
            model_class = apps.get_model(*model.split("."))
        elif issubclass(model, CategoryBase):
            model_class = model
        if model_class is None:
            raise TypeError
    except TypeError:
        raise TemplateSyntaxError("Unknown model submitted: %s" % model)
    return model_class