def evaluate(self):
        self.model_path.set_model(self.expression.models)
        result = None
        try:
            result = self.model_path.get_value()
        except (__HOLE__, AttributeError):
            if self.expression.strict:
                raise TypeError(
                    'Value of {0} is undefined. Set options.strict'
                    ' to false to allow undefined values.'.format(self.path))
        self.value = result
        return self.model_path
dataset/ETHPy150Open openstack/fuel-web/nailgun/nailgun/expression/objects.py/ModelPathWrapper.evaluate