Thanks. If I used Shiny Core would this error not have occurred? I am using Core now, but in the app where I encountered this issue it was written in Express.
It looks like literally doing what the message says works. That is changing the following line from
```python
alt.data_transformers.enable("vegafusion")
```
to
```python
str(alt.data_transformers.e...
In order to use altair for a dataset where the number of rows exceeds 5000, one needs to enable the VegaFusion data transformer. For example, creating the following simple Shiny app:
```python
imp...