docs: 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)