Add todo comment #850

Job	Run time
clang-sanitizers (,thread)	11m 13s
clang-sanitizers (,address,undefined)	11m 35s
downstream	11m 50s
linux-compat (manylinux1-x64)	9m 10s
linux-compat (manylinux1-x86)	9m 22s
linux-compat (manylinux2014-x64)	9m 43s
linux-compat (manylinux2014-x86)	9m 41s
linux-compat (al2-x64)	9m 44s
linux-compat (fedora-34-x64)	10m 37s
linux-compat (opensuse-leap)	12m 16s
linux-compat (rhel8-x64)	11m 38s
linux-shared-libs	10m 27s
linux-compiler-compat (clang-3)	10m 21s
linux-compiler-compat (clang-6)	11m 6s
linux-compiler-compat (clang-8)	10m 57s
linux-compiler-compat (clang-9)	12m 4s
linux-compiler-compat (clang-10)	11m 41s
linux-compiler-compat (clang-11)	10m 39s
linux-compiler-compat (gcc-4.8)	9m 9s
linux-compiler-compat (gcc-5)	9m 56s
linux-compiler-compat (gcc-6)	10m 33s
linux-compiler-compat (gcc-7)	9m 58s
linux-compiler-compat (gcc-8)	10m 30s
osx	10m 31s
windows	11m 24s
windows-app-verifier	14m 58s
windows-shared-libs	11m 9s
windows-vc14 (x86)	9m 56s
windows-vc14 (x64)	10m 17s
	5h 12m 25s

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