collections.In

The SET can be an array, slice, or string.

{{ $s := slice "a" "b" "c" }}
{{ in $s "b" }} → true

{{ $s := slice 1 2 3 }}
{{ in $s 2 }} → true

{{ $s := slice 1.11 2.22 3.33 }}
{{ in $s 2.22 }} → true

{{ $s := "abc" }}
{{ in $s "b" }} → true