'test filters that are themselves expressions'

def test_expr(self):

    t = Template('\n                                ${x    |    myfilter(y)}\n')
    def myfilter(y):
        return (lambda x: ('MYFILTER->%s<-%s' % (x, y)))
    assert (flatten_result(t.render(x='this    is    x', myfilter=myfilter, y='this    is    y')) == 'MYFILTER->this    is    x<-this    is    y')
