new: dev: added ``yaml_get_values`` helper function for charm.

bin/compose-core

@@ -311,6 +311,46 @@ EOF
 export -f merge_yaml_str
 
 
+yaml_get_values() {
+    local sep=${1:-$'\n'} value input type first elt
+    input=$(cat -)
+    if [ -z "$input" ] || [ "$input" == "None" ]; then
+        return 0
+    fi
+    type=$(e "$input" | shyaml get-type)
+    value=
+    case "$type" in
+        "sequence")
+            first=1
+            while read-0 elt; do
+                elt="$(e "$elt" | yaml_get_interpret)" || return 1
+                [ "$elt" ] || continue
+                if [ "$first" ]; then
+                    first=
+                else
+                    value+="$sep"
+                fi
+                first=
+                value+="$elt"
+            done < <(e "$input" | shyaml -y get-values-0)
+            ;;
+        "struct")
+            while read-0 val; do
+                value+=$'\n'"$(e "$val" | yaml_get_interpret)" || return 1
+            done < <(e "$input" | shyaml -y values-0)
+            ;;
+        "NoneType")
+            value=""
+            ;;
+        "str"|*)
+            value+="$(e "$input" | yaml_get_interpret)"
+            ;;
+    esac
+    e "$value"
+}
+export -f yaml_get_values
+
+
 yaml_key_val_str() {
     local entries="$@"