[luatex] documentation typo of `pdf_start_link` whatsit?

[Werner LEMBERG]

>> In `luatex.pdf` (version 1.16 from April 2023), page 142, field
>> `link_attr` of the `pdf_start_link` whatsit is described as being
>> of type 'table'.  Is this correct?  It rather seems to me that it
>> is of type 'string', at least according to what `debugger.lua`
>> reports...
> 
> Both, I guess:

OK, thanks – so there is still something to fix in the
documentation :-)

BTW, how can I display the contents of such a table as a string for
diagnostic purposes on the lua side?  `tostring` doesn't work here; I
just get a hexadicmal address.  Does luatex offer such functionality?
An approximation (i.e., ignoring catcode changes and the like) or
detokenization would be just fine.

```
if type(data) = 'table' then
  output = string_approximation(data)
end
```


   Werner