old_contents: from .simple_broker import (_DataBrokerClass, EventQueue, Header,
                              LocationError, IntegrityError)
  from .handler_registration import register_builtin_handlers
  DataBroker = _DataBrokerClass()  # singleton, used by pims_readers import below
  from .pims_readers import Images, SubtractedImages
  
  register_builtin_handlers()
  
new_contents: from .simple_broker import (_DataBrokerClass, EventQueue, Header,
                              LocationError, IntegrityError, fill_event)
  from .handler_registration import register_builtin_handlers
  DataBroker = _DataBrokerClass()  # singleton, used by pims_readers import below
  from .pims_readers import Images, SubtractedImages
  
  register_builtin_handlers()
  
subject: Put fill_event in the public API.