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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 is_config_var(var):
 """ Checks if the given value is a valid ``file_config.var``. :param var: The value to check :return: True if the given value is a var, otherwise False :rtype: bool """


    return (
        isinstance(var, (attr._make.Attribute, attr._make._CountingAttr))
        and hasattr(var, "metadata")
        and CONFIG_KEY in var.metadata
    )