src/vs/workbench/api/common/extHostDocuments.ts/ExtHostDocuments/getDocument
class ExtHostDocuments:	public getDocument(resource: vscode.Uri): vscode.TextDocument {
		const data = this.getDocumentData(resource);
		if (!data?.document) {
			throw new Error(`Unable to retrieve document from URI '${resource}'`);
		}
		return data.document;
	}