Improve CachedFetcher #129

Job	Run time
apply-label-to-new-pr	2s
check-labels	5s
run-unit-test	53s
find-e2e-tests	4s
pull-docker-image	21s
e2e tests: /home/runner/work/async-substrate-interface/async-substrate-interface/btcli/tests/e2e_tests/test_wallet_interactions.py	3m 17s
e2e tests: /home/runner/work/async-substrate-interface/async-substrate-interface/btcli/tests/e2e_tests/test_children_hotkeys.py	1m 23s
e2e tests: /home/runner/work/async-substrate-interface/async-substrate-interface/btcli/tests/e2e_tests/test_senate.py	3m 23s
e2e tests: /home/runner/work/async-substrate-interface/async-substrate-interface/btcli/tests/e2e_tests/test_staking_sudo.py	3m 44s
e2e tests: /home/runner/work/async-substrate-interface/async-substrate-interface/btcli/tests/e2e_tests/test_unstaking.py	3m 32s
e2e tests: /home/runner/work/async-substrate-interface/async-substrate-interface/btcli/tests/e2e_tests/test_wallet_creations.py	2m 27s
e2e tests: /home/runner/work/async-substrate-interface/async-substrate-interface/btcli/tests/e2e_tests/test_root.py	1m 10s
	20m 21s

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