def all_contents(self):
        """Iterates over all subviews from collections at this view from
        *all* sources. If the object for this view in any source is not
        iterable, then a ConfigTypeError is raised. This method is
        intended to be used when the view indicates a list; this method
        will concatenate the contents of the list from all sources.
        """
        for collection, _ in self.resolve():
            try:
                it = iter(collection)
            except __HOLE__:
                raise ConfigTypeError(
                    u'{0} must be an iterable, not {1}'.format(
                        self.name, type(collection).__name__
                    )
                )
            for value in it:
                yield value

    # Validation and conversion.
dataset/ETHPy150Open beetbox/beets/beets/util/confit.py/ConfigView.all_contents