pandas dataframe sorting

The content saved in Excel with such a key value mapping is as follows

If the text contains a b c, mark it with v3 tag, if it contains a b, mark it with v2 tag, if it only contains a, mark it with v1 tag

Read this Excel that saves this mapping relationship into Pandas how to do this sort

That is, key1, key2, and key3 are not empty in the first row, followed by one empty, and finally two empty

That is, after the above table is sorted, it becomes

Then follow this order to match one by one, hit the previous one, and the latter will no longer match. For example, if it matches a b c, it will no longer match a b and match a. The tag corresponding to the text is v3

Q: How to sort Pandas dataframe like this