Misc: some useful function and new models #635

Job	Run time
Build documentation	2m 13s
conda install latest tensorflow (ubuntu-20.04)	4m 10s
Unit tests (ubuntu-20.04, 3.7)	15m 36s
conda install (ubuntu-20.04)	2m 37s
Unit tests (macos-11, 3.7)	38m 6s
Test uproot3 (ubuntu-20.04, 3.7)	15m 54s
Style checks	2m 9s
Unit tests (ubuntu-20.04, 3.6)	14m 7s
Unit tests (ubuntu-20.04, 3.8)	14m 55s
Coverage (ubuntu-20.04, 3.7)	9s
	1h 49m 56s

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