do_get_fallback explanation

**Which part is this question about**
This is about the `do_get_fallback` method

**Describe your question**
The documentation doesn't really explains this, it just says it can be used if there are additional calls to `do_get`.

Can you explain when and how you would use this?

**Additional context**
None

Start by locating the `do_get_fallback` method and the existing documentation for `do_get`, then read how the fallback relates to additional calls. Update the relevant documentation to explain when and how `do_get_fallback` is used, including enough context for a reader to distinguish it from `do_get`.

Written by the indexing model from the issue text.