How to use the oas-kit-common.hasDuplicates function in oas-kit-common

}
    if (typeof schema.uniqueItems !== 'undefined') {
        should(schema.uniqueItems).be.type('boolean','uniqueItems must be a boolean');
    }
    if (typeof schema.maxProperties !== 'undefined') {
        should(schema.maxProperties).be.type('number','maxProperties must be a number');
        should(schema.maxProperties).be.greaterThan(-1);
    }
    if (typeof schema.minProperties !== 'undefined') {
        should(schema.minProperties).be.type('number','minProperties must be a number');
        should(schema.minProperties).be.greaterThan(-1);
    }
    if (typeof schema.required !== 'undefined') {
        should(schema.required).be.an.Array();
        should(schema.required).not.be.empty();
        should(common.hasDuplicates(schema.required)).be.exactly(false,'required items must be unique: '+common.firstDupe(schema.required));
        // nb: required array can include (for example) specific properties which match patternProperties and which aren't listed in properties
    }
    if (schema.properties) {
        should(schema.properties).be.an.Object();
        should(schema.properties).not.be.an.Array();
    }
    should(schema).not.have.property('patternProperties');
    /*if (schema.patternProperties) {
        should(schema.patternProperties).be.an.Object();
        for (let prop in schema.patternProperties) {
            try {
                let regex = new RegExp(prop);
            }
            catch (ex) {
                should.fail(false,true,'patternProperty '+prop+' does not conform to ECMA-262');
            }