docs: public static String rawTypeToString(TypeMirror type, char innerClassSeparator) {
      if (!(type instanceof DeclaredType)) {
        throw new IllegalArgumentException("Unexpected type: " + type);
      }
      StringBuilder result = new StringBuilder();
      DeclaredType declaredType = (DeclaredType) type;
      rawTypeToString(result, (TypeElement) declaredType.asElement(), innerClassSeparator);
      return result.toString();
    }