[BUG] Repeated warnings "Number of requested results 20 is greater than number of elements in index 3, updating n_results = 3"

[oshoma]

Describe the bug
When running the Sherpa tutorial I see repeated warnings in my terminal:

"Number of requested results 20 is greater than number of elements in index 3, updating n_results = 3" .

I'm not sure where these are coming from or whether they are benign.

To Reproduce
Steps to reproduce the behavior:

1. Set up the sherpa tutorial as per the steps in docs/How_To/Tutorials/document_reader.rst

2. Copy this file as paper.pdf in your tutorial directory
   paper.pdf

3. Run sherpa PDF reader: python main.py --config agent_config.yml

4. See the warnings on the command line output

Expected behavior
The tutorial should run without this warning.