Fix error in MetricsApp's display() method

[Gooogr]

Description

• Fix code error local variable fig_widget referenced before assignment after calling display() method of MetricsApp instance.
• Fix nbformat error after extracting plotly figure from chart. Add nbformat to project dependencies

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Optimization

How Has This Been Tested?

Before submitting a PR, please check yourself against the following list. It would save us quite a lot of time.

• Have you read the contribution guide?
• Have you updated the relevant docstrings? We're using Numpy format, please double-check yourself
• Does your change require any new tests?
• Have you updated the changelog file?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (9b3992e) to head (01a4e48).
Report is 70 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##              main      #169     +/-   ##
===========================================
  Coverage   100.00%   100.00%             
===========================================
  Files           45        56     +11     
  Lines         2242      3446   +1204     
===========================================
+ Hits          2242      3446   +1204     

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