code: @Nonnull
      public static String toUniqueString(@Nonnull TypeMirror t) {
          StringBuilderAndState<TypeMirror> state = new StringBuilderAndState<>();
          t.accept(toUniqueStringVisitor, state);
          return state.bld.toString();
      }
docs: Represents the type mirror as a string in such a way that it can be used for equality comparisons.
  
  @param t type to convert to string
  @return the string representation of the type that is fit for equality comparisons