React error report solution!

Warning: Encountered two children with the same key, `.$4`. Keys should be unique so that components maintain their identity across updates. Non-unique keys may cause children to be duplicated and/or omitted  the behavior is unsupported and could change in a future version.
    in ul (created by DOMWrap)
    in DOMWrap (created by Menu)
    in Provider (created by Menu)
    in Menu (created by Menu)
    in Menu (created by Left)
    in div (created by Sider)
    in div (created by Sider)
    in Sider (created by Left)
    in Left (created by Main)
    in div (created by BasicLayout)
    in BasicLayout (created by Adapter)
    in Adapter (created by Main)
    in Main (created by Connect(Main))
    in Connect(Main) (created by Route)
    in Route
    in Switch
    in Router
    in Provider
    in Unknown
    
    
    react    
    
    
     Key

Javascript react.js html5 node.js redux

Mar.01,2021

you use the same key:'.$4',key as the logo, and you cannot repeat

this is warning, not error, because you traverse and render an array of elements, and then the key of the elements is the same.

see a lot of similar problems, why not read these messages? Is it because you can't read English, or is it for some reason?
my English PE teacher teaches me, so I can guess.

has the landlord solved it? I also encountered this problem, but there is no key on my page

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