PythonLibrary.useVersion can only be used to select the Python-library-version-to-load before any usages of Python. It does not support dynamically swift Python version - more context in
However, the name useVersion is misleading - people may believe that it can be used to dynamically switch Python version.
To catch some misuses, a precondition error should be produced when PythonLibrary.useVersion is called for the second time.
(Note: the ideal precondition error is "PythonLibrary.useVersion" should not be called after any Python library symbols have been loaded.)