src/vs/workbench/contrib/debug/common/abstractDebugAdapter.ts/AbstractDebugAdapter/onEvent
class AbstractDebugAdapter:	onEvent(callback: (event: DebugProtocol.Event) => void): void {
		if (this.eventCallback) {
			this._onError.fire(new Error(`attempt to set more than one 'Event' callback`));
		}
		this.eventCallback = callback;
	}