Never returning when using folium's png export

```julia
using PyCall
flm = pyimport("folium") # Python package that could be installed through something like `python3 -m pip install folium `
m = flm.Map(location=[40.761405212565364, -73.98312095111525], zoom_start=16)
data = m._to_png(5)
```
The last statement `m._to_png(5)` blocks the REPL and never exists.

the equivalent pure python code, works with no issue. I am not sure what is going on here!

```python
import folium as flm
m = flm.Map(location=(40.761405212565364, -73.98312095111525), zoom_start=16)
data = m._to_png(5)
```