Add typing in signer.py #238

Job	Run time
Test on python 3.7 and ubuntu-latest	2m 5s
Test on python 3.7 and windows-latest	2m 39s
Test on python 3.7 and macos-latest	32s
Test on python 3.8 and ubuntu-latest	1m 52s
Test on python 3.8 and windows-latest	2m 28s
Test on python 3.8 and macos-latest	25s
Test on python 3.9 and ubuntu-latest	1m 48s
Test on python 3.9 and windows-latest	2m 37s
Test on python 3.9 and macos-latest	26s
Test on python 3.10 and ubuntu-latest	2m 8s
Test on python 3.10 and windows-latest	2m 4s
Test on python 3.10 and macos-latest	25s
Test on python 3.11 and ubuntu-latest	1m 30s
Test on python 3.11 and windows-latest	2m 38s
Test on python 3.11 and macos-latest	17s
Test on python 3.12 and ubuntu-latest	1m 54s
Test on python 3.12 and windows-latest	2m 23s
Test on python 3.12 and macos-latest	34s
	28m 45s

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