By having a 'regular' python output stream, it is possible to e.g. redirect that to a string, or suppress it in notebooks. See https://pybind11.readthedocs.io/en/stable/advanced/pycpp/utilities.html#capturing-standard-output-from-ostream
In the longer term, it may be desirable to wrap the aocommon::Logger with a python logger, with all bells and whistles. But that's another story.