src/vs/workbench/api/common/extHostNotebookEditor.ts/ExtHostNotebookEditor/setDecorations
class ExtHostNotebookEditor:	setDecorations(decorationType: vscode.NotebookEditorDecorationType, range: vscode.NotebookRange): void {
		if (range.isEmpty && !this._hasDecorationsForKey.has(decorationType.key)) {
			// avoid no-op call to the renderer
			return;
		}
		if (range.isEmpty) {
			this._hasDecorationsForKey.delete(decorationType.key);
		} else {
			this._hasDecorationsForKey.add(decorationType.key);
		}

		return this._proxy.$trySetDecorations(
			this.id,
			extHostConverter.NotebookRange.from(range),
			decorationType.key
		);
	}