Functions in context cannot be called

Created by: duncte123

With the following setup

    app.get('/', (req, res) => {
        twing.render('index.twig', { coolFN: () => { /* some logic */ return false; } }).then((output) => {
            res.end(output);
        });
    });

and the following template

{% if coolFN() %}
    Yes it is cool
{% else %}
    not cool
{% endif %}

the following exception occurs

/mnt/d/development/javascript/emotional-support/node_modules/twing/dist/cjs/lib/parser.js:918
            let e = new syntax_1.TwingErrorSyntax(`Unknown "${name}" function.`, line, this.getStream().getSourceContext());
                    ^

TwingErrorSyntax: Unknown "coolFN" function in "index.twig" at line 1.
    at TwingParser.getFunctionExpressionFactory (/mnt/d/development/javascript/emotional-support/node_modules/twing/dist/cjs/lib/parser.js:918:21)
    at TwingParser.getFunctionNode (/mnt/d/development/javascript/emotional-support/node_modules/twing/dist/cjs/lib/parser.js:569:41)
    at TwingParser.parsePrimaryExpression (/mnt/d/development/javascript/emotional-support/node_modules/twing/dist/cjs/lib/parser.js:488:41)
    at TwingParser.getPrimary (/mnt/d/development/javascript/emotional-support/node_modules/twing/dist/cjs/lib/parser.js:463:21)
    at TwingParser.parseExpression (/mnt/d/development/javascript/emotional-support/node_modules/twing/dist/cjs/lib/parser.js:366:25)
    at TwingTokenParserIf.parse (/mnt/d/development/javascript/emotional-support/node_modules/twing/dist/cjs/lib/token-parser/if.js:24:32)
    at TwingParser.subparse (/mnt/d/development/javascript/emotional-support/node_modules/twing/dist/cjs/lib/parser.js:175:42)
    at TwingTokenParserIf.parse (/mnt/d/development/javascript/emotional-support/node_modules/twing/dist/cjs/lib/token-parser/if.js:28:32)
    at TwingParser.subparse (/mnt/d/development/javascript/emotional-support/node_modules/twing/dist/cjs/lib/parser.js:175:42)
    at TwingTokenParserBlock.parse (/mnt/d/development/javascript/emotional-support/node_modules/twing/dist/cjs/lib/token-parser/block.js:35:32) {
  rawMessage: 'Unknown "coolFN" function.',
  .... long script ....

I am making use of the experimental modules but I don't think that this is an issue

nodejs version: v15.0.1