## Description
When we created `Z6004/Wikidata lexeme form`, we decided to have a key `Z6004K2/lexeme`, which refers to the containing lexeme (Even though that element is not present in the JSON that Wikidata delivers to us, it's trivial to insert it in the ZObject). Unfortunately, we neglected to include a similar key in `Z6006/Wikidata lexeme sense`, so we have an inconsistent treatment of these 2 types. The inconsistency is somewhat jarring because the types are very similar In most respects. Also, since an instance of `Z6006` can exist independently of its containing lexeme, indicating the identity of the lexeme, as we do in `Z6004`, would be an appropriate convenience.
* [x] Decide whether to shift the existing keys so that the new key could be K2.
** Decision: we will shift; the new key will be K4.
* [] Update the definition of `Z6006` in function-schemata.
* [] Update the ZObject-construction code in the orchestrator.
** Adds to the output of `Z6826/Fetch Wikidata lexeme sense` and `Z6825/Fetch Wikidata lexeme`
* [] Front-end: Update `Wikidata lexeme sense component` to handle `K4`
* [x] If we choose to shift the existing keys, correct all existing functions that refer to the existing keys.
** At present there are about 6 such functions showing up in Wikifunctions search results.
After deployment, functions can start using `K4` without changing any pre-existing code.
**Desired behavior/Acceptance criteria (returned value, expected error, performance expectations, etc.)**
* ...
---
## Completion checklist
* [ ] Before closing this task, review one by one the checklist available here: https://www.mediawiki.org/wiki/Abstract_Wikipedia_team/Definition_of_Done#Back-end_Task/Bug_completion_checklist