Marqo _highlights return type differs between LEXICAL and TENSOR search
## Problem
The `_highlights` field in Marqo search results had different types depending on the search method. Reading `results['hits'][0]['_highlights']` returned a dict for the default TENSOR search but an empty list for `search_method='LEXICAL'`. This made client code that consumed highlights method-dependent and fragile. A community member proposed the fix and a maintainer invited a PR.
## Verified fix
This inconsistency was fixed in Marqo v2, where the `_highlights` return type was made consistent across search methods. If you are on Marqo v1, the workaround is to handle both types client-side; upgrading to v2 resolves it.
Source: https://github.com/marqo-ai/marqo/issues/70