Unicode plugin function hexToKey is not working

I tried to put hexToKey in my keymap and it is giving me compiler errors.

First I tried as Unicode.hexToKey(0x0087) and it said the Unicode object had no such function.

Then I tried as hexToKey(0x0087) and I got the following:

exit status 1
call to non-'constexpr' function 'Key hexToKey(uint8_t)'

How can I get this to work?