def _tree(self, type):
    if (type == 'single'):
        return MockProviderSingle(self._default_collection)._get_tree(isbn=self.SINGLE_ISBN)
    else:
        return MockProviderMulti(self._default_collection)._get_tree(isbn=self.MULTI_ISBN)
def _tree(self, type):
    if (type == 'single'):
        return MockProviderSingle(self._default_collection)._get_tree(isbn=self.SINGLE_ISBN)
    else:
        return MockProviderMulti(self._default_collection)._get_tree(isbn=self.MULTI_ISBN)