Created CommaList type

internal/codegen/codegen.go

@@ -71,8 +71,7 @@ var attribTypes = map[string]AttribTypeInfo{
 		Template: simpleTemplate("...string", "SpaceList(%s).String()"),
 	},
 	"comma list": {
-		Template: listTemplate(","),
-		Imports:  []string{"strings"},
+		Template: simpleTemplate("...string", "CommaList(%s).String()"),
 	},
 }