def conceptFor(self, observer):
        if observer is self.actor:
            msg = self.actorMessage
        elif observer is self.target:
            msg = self.targetMessage
        elif observer is self.tool:
            msg = self.toolMessage
        else:
            msg = self.otherMessage
        return msg
Retrieve the appropriate L{IConcept} provider for a given observer.  If
dataset/ETHPy150Open twisted/imaginary/imaginary/events.py/Event.conceptFor