src/vs/workbench/api/common/extHostNotebookEditor.ts/NotebookEditorCellEditBuilder/replaceMetadata
class NotebookEditorCellEditBuilder:	replaceMetadata(value: { [key: string]: any }): void {
		this._throwIfFinalized();
		this._collectedEdits.push({
			editType: CellEditType.DocumentMetadata,
			metadata: value
		});
	}