Saving a figure to file - Error with QApplication and QObject::startTimer

I have a problem with my streamlit app. I am trying to generate an image and save it to a file, which is then downloaded via the app. I do not need the figure to be displayed in the streamlit app.

When I run the app I get the following message, even though the image is created and saved in the appropriate place.

WARNING: QApplication was not created in the main() thread.

Then, if I run the app a second time I get the following error with only a blank image saved.

QObject::startTimer: Timers can only be used with threads started with QThread

I am plotting the figure using a package called ete3, which generates trees. These are then saved to PNG, PDF or SVG files.

I realise that my problem relates more to this package but I do not get any error when I generate the figure in a script outside of streamlit, so I hope some streamlit people could point me in the right direction please!

I’m using Streamlit v1.12.0/Python 3.9.13/Conda/MacOS 11.6

Here is a minimal reproducible example:

st.title('Click button to generate figure. Error appears on command line.')
form = st.form(key="submit_form")
with form:
    submitted = st.form_submit_button(label="Submit")
if not submitted:
t = Tree( "((a,b),c);" )

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