It would be helpful to make it clear in section "Configuration file format" that it's not possible to configure filters through configuration file as opposed to dictionary passed to dictConfig() method.
I found this clearly stated in Pyramid docs at http://docs.pylonsproject.org/docs/pyramid/en/latest/narr/logging.html – "For more advanced filtering, the logging module provides a logging.Filter object; however it cannot be used directly from the configuration file."