src/vs/workbench/api/common/extHostTypeConverters.ts/isLegacyRelativePatternShape
	function isLegacyRelativePatternShape(obj: unknown): obj is { base: string; pattern: string } {

		// Before 1.64.x, `RelativePattern` did not have any `baseUri: Uri`
		// property. To preserve backwards compatibility with older extensions
		// we allow this old format when creating the `vscode.RelativePattern`.

		const rp = obj as { base: string; pattern: string } | undefined | null;
		if (!rp) {
			return false;
		}

		return typeof rp.base === 'string' && typeof rp.pattern === 'string';
	}