Function bash_kvpair_string 

pub fn bash_kvpair_string(shape: &BashParamShape<'_>) -> String

bash ${var@K} — like @Q for a scalar; for an array, key "value" pairs in ONE word.

$ bash -c 'a=(x "y z");          printf "<%s>" "${a[@]@K}"' → <0 "x" 1 "y z">
$ bash -c 'declare -A h=([q]=1); printf "<%s>" "${h[*]@K}"' → <q "1" >