def is_safe_callable(self, obj):
        return not (getattr(obj, 'unsafe_callable', False) or
                    getattr(obj, 'alters_data', False))
Check if an object is safely callable.  Per default a function is
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/jinja2-2.6/jinja2/sandbox.py/SandboxedEnvironment.is_safe_callable