text: Title: How to change model for indexing?
  Body: gpt3 sucks at math and code! I'm trying to use gpt4 for indexing but with no luck. It'd be great if there was a model parameter for indexing commands. currently, it only supports while querying which is not helpful if the context is written using gpt3. 
  
  I also tried setting the settings parameter model to gpt-4 but it didn't seem to work.
  