Explicitly convert to Symbol when doing expression parsing

[Vaibhavdixit02]

No description provided.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 17.60%. Comparing base (43f93d0) to head (07d4147).
⚠️ Report is 2071 commits behind head on master.

Files with missing lines	Patch %	Lines
src/parsing.jl	0.00%	2 Missing ⚠️
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HEAD has 2 uploads less than BASE

Flag	BASE (43f93d0)	HEAD (07d4147)
	4	2

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #1017       +/-   ##
===========================================
- Coverage   77.99%   17.60%   -60.40%     
===========================================
  Files          28       28               
  Lines        3381     3335       -46     
===========================================
- Hits         2637      587     -2050     
- Misses        744     2748     +2004     

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[ChrisRackauckas]

Needs a test