src/vs/workbench/api/common/extHostDiagnostics.ts/DiagnosticCollection/forEach
class DiagnosticCollection:	forEach(callback: (uri: URI, diagnostics: ReadonlyArray<vscode.Diagnostic>, collection: DiagnosticCollection) => any, thisArg?: any): void {
		this._checkDisposed();
		for (let uri of this.#data.keys()) {
			callback.apply(thisArg, [uri, this.get(uri), this]);
		}
	}