text: Title: [DOC] Fix type annotation issues in documentation 
  Body: Two things that can be improved:
  
  1) Type annotations in the docs hurt readability 
  
  This is an example:
  
  ![image](https://user-images.githubusercontent.com/4762711/66703876-25f52700-ece5-11e9-8199-9f4d67767ad6.png)
  
  I think we could alleviate this quite a bit by bolding the actual parameters names or something akin to that.
  
  2) Abbreviated descriptions on the functions list page do weird things with type annotations and cut info out:
  
  ![image](https://user-images.githubusercontent.com/4762711/66703872-1d045580-ece5-11e9-99bd-096c8b497f25.png)
  
  It might make sense to exclude type annotations here entirely.