N3 proof engine inspired by http://www.openbookproject.net/py4fun/prolog/prolog3.py
and is with depth first search and euler path anti-looping detection.
Thanks to Tim Berners-Lee and Dan Connolly for inventing N3 and for creating N3
Usage: python3 eye.py [–why] [–once] [–debug] triples
Test: python3 eye.py –why https://josd.github.io/eye/looking/eye.py/tree.n3
Remark that the N3 that is actually understood is very limited:
qnames, () lists, facts and => rules on a single line and not yet  ; , ^ ! ^^ @