FIX: Exception error for multiple design

[ramin4667]

Description

This PR raises an exception for multiple design definitions with an already opened design.

Issue linked

NA

Checklist

• I have tested my changes locally.
• I have added necessary documentation or updated existing documentation.
• I have followed the coding style guidelines of this project.
• I have added appropriate tests (unit, integration, system).
• I have reviewed my changes before submitting this pull request.
• I have linked the issue or issues that are solved by the PR if any.
• I have agreed with the Contributor License Agreement (CLA).

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.13%. Comparing base (979f6c2) to head (6d4155f).
Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5937   +/-   ##
=======================================
  Coverage   85.13%   85.13%           
=======================================
  Files         167      167           
  Lines       63042    63042           
=======================================
+ Hits        53672    53673    +1     
+ Misses       9370     9369    -1     

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[myoung301]

@ramin4667 I think the code looks good. Can you add a unit test that will exercise the exception and the close method?