remove unused function #737

Job	Run time
downstream	2m 22s
clang-sanitizers (,thread)	2m 51s
linux-compat (manylinux2014-x64)	2m 21s
clang-sanitizers (,address,undefined)	3m 1s
linux-compat (manylinux2014-x86)	2m 15s
linux-compat (fedora-34-x64)	2m 10s
linux-compiler-compat (clang-3)	2m 28s
linux-compat (opensuse-leap)	3m 2s
linux-compiler-compat (clang-6)	2m 59s
linux-shared-libs	2m 15s
linux-compat (rhel8-x64)	2m 36s
linux-compiler-compat (clang-8)	3m 47s
linux-compat (al2-x64)	2m 13s
linux-compiler-compat (clang-9)	3m 52s
linux-compiler-compat (clang-10)	3m 2s
osx	2m 11s
linux-compiler-compat (clang-11)	3m 12s
linux-compiler-compat (gcc-4.8)	2m 22s
windows	4m 17s
linux-compiler-compat (gcc-5)	2m 20s
windows-shared-libs	4m 23s
linux-compiler-compat (gcc-6)	2m 29s
linux-compiler-compat (gcc-7)	2m 32s
windows-vc14 (x86)	3m 4s
linux-compiler-compat (gcc-8)	3m 2s
windows-vc14 (x64)	5m 15s
	1h 16m 21s

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