def test_lookup(self):
        assert event.Priority.lookup(event.Priority.CORE) is event.Priority.CORE
        assert event.Priority.lookup(event.Priority.CORE.value) is event.Priority.CORE
        assert event.Priority.lookup(-12312412) == -12312412
def dfs_print(root):
        if root is None:
            return
        dfs_print(root.left)
        print(str(root.key) + ' ', end='')
        dfs_print(root.right)