You have to update the package traitlets to traitlets-5.14.3

Indeed traitlets-5.14.1:

• contains a bug, trandforming 'png' into {'g', 'n', 'p'} , since (traitlets-5.13.0 ?)
• causing endless graphic problems in spyder console.

Due to this bug: ipython/traitlets#903

example of method: #1587 (comment)

pip install --upgrade traitlets