def pre_tracer(self, obj, name, old, new, handler):
        indent = self.indent
        time = datetime.utcnow().isoformat(' ')
        container = self.container
        container.record(
            ChangeMessageRecord(
                time=time,
                indent=indent,
                name=name,
                old=old,
                new=new,
                class_name=obj.__class__.__name__,
            ),
        )

        container.record(
            CallingMessageRecord(
                time=time,
                indent=indent,
                handler=handler.__name__,
                source=inspect.getsourcefile(handler),
            ),
        )
        self.indent += 1
Record a string representation of the trait change dispatch
dataset/ETHPy150Open enthought/traits/traits/util/event_tracer.py/ChangeEventRecorder.pre_tracer