Add doctest #604

Job	Run time
Julia 1.0 - ubuntu-latest - x64	3m 25s
Julia 1.0 - macos-latest - x64	4m 28s
Julia 1.0 - windows-latest - x64	7m 32s
Julia 1.6 - ubuntu-latest - x64	3m 28s
Julia 1.6 - macos-latest - x64	5m 12s
Julia 1.6 - windows-latest - x64	12m 43s
Julia 1.10 - ubuntu-latest - x64	2m 46s
Julia 1.10 - macos-latest - x64	3m 33s
Julia 1.10 - windows-latest - x64	3m 31s
Julia 1 - ubuntu-latest - x64	4m 20s
Julia 1 - macos-latest - x64	5m 42s
Julia 1 - windows-latest - x64	5m 23s
Julia nightly - ubuntu-latest - x64	4m 18s
Julia nightly - macos-latest - x64	4m 38s
Julia nightly - windows-latest - x64	4m 57s
	1h 15m 56s

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