i met warning and it said i have to report to dev

im running the examples provided in the main github page and it return this for the second code:
```
WARNING (please report to programinduction devs): likelihood unification failure against expr=nand (tp=bool → bool → bool) for f=nand frag_tp=bool → bool → bool tmpl_tp=t1 → t0 → bool xs=["(nand $0 $0)", "(nand $1 $1)"]
```