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Add a listener to a specific event, that will only be invoked once
Signature:
once<K extends keyof E>(eventName: K): Promise<E[K]>;
| Parameter | Type | Description | 
|---|---|---|
| eventName | K | The name of the event | 
Returns:
Promise<E[K]>
After the first occurrence of the specified event, the listener will be invoked and immediately removed.