Here is a small repro based on that package:
exportdefaultclassFileReaderimplementsObservable{set(option: Record<string,unknown>): void;set(name: string,value: unknown): void;}exportinterfaceObservable{set(...args: [option: Record<string,unknown>]|[name: string,value: unknown]|[name: string]): void;}
Here is a small repro based on that package: