update copyright

add examples to CacheClient docstring

From: @taroxd
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From: @wtcheng
Reviewed-by: @guoqi1024,@kisnwang
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From: @yeyunpeng2020
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From: @caojian05
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fix rebase confict

From: @luoyang42
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From: @yangzhenzhang
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From: @zhanghuiyao
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