How to use the @rxweb/reactive-form-validators.RxwebValidators.greaterThan function in @rxweb/reactive-form-validators

() => {
          let formBuilder = new FormBuilder();
          let formGroup = formBuilder.group({
'age':[18],
            'voterAge':19
          });
          expect(RxwebValidators.greaterThan({fieldName:'age',conditionalExpression:'x => x.age > 17'})(formGroup.controls.voterAge)).toBeNull()
        });

ngOnInit() {
        this.userFormGroup = this.formBuilder.group({
            age:['',], 
            voterAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,conditionalExpression:'x => x.age > 17' })], 
            memberAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,conditionalExpression:(x,y) => x.age > 17  })], 
        });
    }
}

ngOnInit() {
        this.userFormGroup = this.formBuilder.group({
            age:['',], 
            memberAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,conditionalExpression:(x,y) => x.age > 17  })], 
            voterAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,conditionalExpression:'x => x.age > 17' })], 
            otherAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,message:'Please enter number greater than 0.' })], 
        });
    }
}

ngOnInit() {
        this.userFormGroup = this.formBuilder.group({
            age:['',], 
            voterAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,conditionalExpression:'x => x.age > 17' })], 
            memberAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,conditionalExpression:(x,y) => x.age > 17  })], 
        });
    }
}

ngOnInit() {
        this.userFormGroup = this.formBuilder.group({
            age:['',], 
            voterAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,conditionalExpression:'x => x.age > 17' })], 
            otherAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,message:'Please enter number greater than 0.' })], 
        });
    }
}

ngOnInit() {
        this.userFormGroup = this.formBuilder.group({
            age:['',], 
            memberAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,conditionalExpression:(x,y) => x.age > 17  })], 
            voterAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,conditionalExpression:'x => x.age > 17' })], 
            otherAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,message:'Please enter number greater than 0.' })], 
        });
    }
}

ngOnInit() {
        this.userFormGroup = this.formBuilder.group({
            age:['',], 
            voterAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,conditionalExpression:'x => x.age > 17' })], 
            memberAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,conditionalExpression:(x,y) => x.age > 17  })], 
        });
    }
}

ngOnInit() {
        this.userFormGroup = this.formBuilder.group({
            age:['',], 
            voterAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,conditionalExpression:'x => x.age > 17' })], 
            memberAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,conditionalExpression:(x,y) => x.age > 17  })], 
        });
    }
}

ngOnInit() {
        this.userFormGroup = this.formBuilder.group({
            age:['',], 
            voterAge:['', RxwebValidators.greaterThan({fieldName:'age' })], 
        });
    }
}

ngOnInit() {
        this.userFormGroup = this.formBuilder.group({
            age:['',], 
            voterAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,conditionalExpression:'x => x.age > 17' })], 
            otherAge:['', RxwebValidators.greaterThan({fieldName:'age'  ,message:'Please enter number greater than 0.' })], 
        });
    }
}