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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_instance_key(self, host, namespace, wmi_class, other=None):
 """ Return an index key for a given instance. Useful for caching. """

        if other:
            return "{host}:{namespace}:{wmi_class}-{other}".format(
                host=host, namespace=namespace, wmi_class=wmi_class, other=other
            )

        return "{host}:{namespace}:{wmi_class}".format(host=host, namespace=namespace, wmi_class=wmi_class)