Is the function string_ends() gone from relations?

I've noticed that when I examine the relations in my start part I made few months ago, there is inserted into the text a red arrow with a cryptic error:

->Invalid data type combination at left side of expression

I couldn't really understand it and so I tried to restart from scratch.  But now when I write this sample relation into an empty part:

if string_ends(MY_FILENAME_STRING,"prt")

   MY_FILENAME_TYPE = "PART"

endif

and try to save, the system says "Relations have errors"

and there is a less cryptic error flagged with a red arrow inserted into the text like this:

if string_ends(MY_FILENAME_STRING,"prt")

-> Invalid symbol 'string_ends' found

   MY_FILENAME_TYPE = "PART"

endif

My first guess is that the function has been removed from Creo 2.0 (M160)?  This is because it doesn't show up in the available functions list.  But this post shows that function used to be in this list in 2014...

Is string_length() still a valid relation function?

But I'm also thinking that's so unlike PTC as they keep everything for the sake of backward compatiblity...

So is there something I'm missing here?