Suppport generators in expand #610

Job	Run time
Julia lts - ubuntu-latest - x64 - pull_request	6m 57s
Julia lts - windows-latest - x64 - pull_request	10m 11s
Julia 1 - windows-latest - x64 - pull_request	13m 50s
Julia 1 - macOS-latest - x64 - pull_request	16m 14s
Julia 1 - ubuntu-latest - x64 - pull_request	11m 30s
Julia lts - macOS-latest - x64 - pull_request	15m 37s
	1h 14m 19s

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