lib/less/visitors/to-css-visitor.js
function hasFakeRuleset(atRuleNode) {
            var bodyRules = atRuleNode.rules;
            return bodyRules.length === 1 && (!bodyRules[0].paths || bodyRules[0].paths.length === 0);
        }
function hasFakeRuleset(atRuleNode) {
            var bodyRules = atRuleNode.rules;
            return bodyRules.length === 1 && (!bodyRules[0].paths || bodyRules[0].paths.length === 0);
        }
if there is only one nested ruleset and that one has no path, then it is just fake ruleset