Add some comments to transform class. #5129

Job	Run time
Code Hygiene	2m 0s
Integration tests (ubuntu-latest)	4m 59s
Build tests (ubuntu-latest)	3m 42s
Integration tests (windows-latest)	6m 21s
Build tests (windows-latest)	4m 51s
Unit tests and Coverage	1m 55s
Render tests (ubuntu-latest, 0)	8m 31s
Render tests (ubuntu-latest, 1)	7m 11s
Render tests (ubuntu-latest, 2)	6m 44s
Render tests (windows-latest, 0)	10m 8s
Render tests (windows-latest, 1)	8m 38s
Render tests (windows-latest, 2)	7m 42s
	1h 12m 42s

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