Why are Instance methods not instrumented

https://github.com/google/atheris/blob/33a1322dadaf4d561f7c99b5641cb33748d4036c/src/instrument_bytecode.py#L1196

I have such observation that code instrumentation does not apply to instance methods. I wonder if this is a TODO of this project or there are some reasons that such functions should not be instrumented. I am trying to learn testing program and this project. Many thanks for any explainations.