Incorrectly parses "NOT something"

[carcinocron]

bash:

echo 'console.log(JSON.stringify(require("@financial-times/n-search-parser").parse("NOT something")))' | node

output:

{"left":null,"operator":"<implicit>","right":{"type":"word","text":"something","offset":4,"length":9}}

In this scenario, I would expect operator to be "NOT".