public boolean isJavaFunction() {
        return type == Type.JAVA_FUNCTION;
    }
@Test
    void testJavaFunction() {
        Variable v = new Variable((Function<String, String>) this::simpleFunction);
        assertTrue(v.isJavaFunction());
        v = new Variable((BiFunction<String, String, String>) this::simpleBiFunction);
        // maybe we are ok with this, karate "call" can be used only with functions
        assertFalse(v.isJavaFunction());        
    }