Optimize sqlparse.utils.imt().

[adamchainz]

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Profiling a sqlparse.parse() on a bunch of large SELECT queries, 14ms out of 59ms, or ~24% of the time, was spent in sqlparse.utils.imt().

Looking at that function, it did some moving of the m and t parameters into lists, wasting work when they’re not set or a single element which can use a faster check. To mitigate this, I optimized it to do the check only when the parameters are set, and avoid the listification of single elements.

This doubled its speed, saving 7ms in the same profile.

[codecov]

Codecov Report

Attention: Patch coverage is 85.71429% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 96.92%. Comparing base (60486b9) to head (e7eab4c).

Files	Patch %	Lines
sqlparse/utils.py	85.71%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #766      +/-   ##
==========================================
- Coverage   97.04%   96.92%   -0.12%     
==========================================
  Files          20       20              
  Lines        1558     1563       +5     
==========================================
+ Hits         1512     1515       +3     
- Misses         46       48       +2     

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[andialbrecht]

Thanks for the patch! That makes the code much more readable as well.