Adding matrix model example

[kjjarvis]

Added example of creating a matrix model in notebook 04. New Models

[github-actions[bot]]

Thank you for opening this PR. Each PR into dev requires a code review. For the code review, look at the following:

• [ ] Reviewer (someone other than author) should look for bugs, efficiency, readability, testing, and coverage in examples (if relevant).
• [ ] Ensure that each PR adding a new feature should include a test verifying that feature.
• [ ] All errors from static analysis must be resolved.
• [ ] Review the test coverage reports (if there is a change) - will be added as comment on PR if there is a change
• [ ] Review the software benchmarking results (if there is a change) - will be added as comment on PR
• [ ] Any added dependencies are included in requirements.txt, setup.py, and dev_guide.rst (this document)
• [ ] All warnings from static analysis must be reviewed and resolved - if deemed appropriate.

[codecov-commenter]

Codecov Report

Merging #102 (e01a60b) into dev (d281481) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev     #102   +/-   ##
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  Coverage   84.19%   84.19%           
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  Files          99       99           
  Lines       10183    10183           
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  Hits         8574     8574           
  Misses       1609     1609