Failed to resolve component: transition-group

[natolee]

When I run my program, the console shows some warn messages as followings:

[Vue warn]: Failed to resolve component: transition
at
at <VueTreeselect multiple=true options= (1) [Proxy] noResultsText="No results..." ... >
at
at <Home onVnodeUnmounted=fn ref=Ref< undefined > >
at
at
[Vue warn]: Failed to resolve component: transition-group
at
at
at <VueTreeselect multiple=true options= (1) [Proxy] noResultsText="No results..." ... >
at
at <Home onVnodeUnmounted=fn ref=Ref< Proxy {_: , $: , $el: , $data: , $props: , …} > >
at
at

How can I fix it?