'L{Tag.clear} removes all children from a tag, but leaves its attributes
in place.'

def test_clear(self):

    tag = proto('these    are', 'children', 'cool', andSoIs='this-attribute')
    tag.clear()
    self.assertEqual(tag.children, [])
    self.assertEqual(tag.attributes, {'andSoIs': 'this-attribute'})
