extensions/markdown-language-features/src/languageFeatures/dropIntoEditor.ts/getParentDocumentUri
export function getParentDocumentUri(document: vscode.TextDocument): vscode.Uri {
	if (document.uri.scheme === Schemes.notebookCell) {
		for (const notebook of vscode.workspace.notebookDocuments) {
			for (const cell of notebook.getCells()) {
				if (cell.document === document) {
					return notebook.uri;
				}
			}
		}
	}

	return document.uri;
}