generator/src/org/immutables/generator/TypeHierarchyCollector.java
protected String stringify(DeclaredType input, TypevarContext context) {
    return toTypeElement(input).getQualifiedName().toString();
  }
protected String stringify(DeclaredType input, TypevarContext context) {
    return toTypeElement(input).getQualifiedName().toString();
  }
overridable stringify.
@param input the input
@param context the context
@return the string