Iterate all fields as a sequence of (path,name,value) tuples.

        :return:

def iter_fields(self):
        """
        Iterate all fields as a sequence of (path,name,value) tuples.

        :return:
        """
        def generator(path, values):
            for name,value in sorted(values.items()):
                if isinstance(value, ValueTree):
                    for inner in generator(path + name, value._values):
                        yield inner
                else:
                    yield (path, name, value)
        return generator(Path([]), self._values)