'flatatt() does not modify the dict passed in.'

def test_flatatt_no_side_effects(self):

    attrs = {'foo': 'bar', 'true': True, 'false': False}
    attrs_copy = copy.copy(attrs)
    self.assertEqual(attrs, attrs_copy)
    first_run = flatatt(attrs)
    self.assertEqual(attrs, attrs_copy)
    self.assertEqual(first_run, '    foo="bar"    true')
    second_run = flatatt(attrs)
    self.assertEqual(attrs, attrs_copy)
    self.assertEqual(first_run, second_run)
