I would say `return stm == "Template"` is enough.

Because with these tests you do that: 

* first exclude non-existing statements, which non-valid names
* then exclude all statement names that correspond to widgets
* finally exclude all statement names that are not `"Template"`

You can keep the first test if you want to specifically return `null` if it is not a valid statement, but I would leave the responsibility to the user to do the check himself. Otherwise, add to the JSDoc the fact this method can return `null`.