Protractor: how I can rightly use filtering in Protractor?

I try to start testing with protractor and now I have a problem, that I can't solve.

I have this test:

 describe('Test_3', function() {
    var my_url = 'http://wks-15103:8010/ps/ng-components/examples/ps-checkbox.html'
    var main_checkbox = element(by.xpath("//div[@ng-model='My_Group']/div[1]/span/span[1]"));
    var checkbox_list = element.all(by.xpath("//div[@ng-model='My_Group']/div[2]/div/span/span[1]")); 
    var title_checkbox_list = element.all(by.xpath("//div[@ng-model='My_Group']/div[2]/div/span"));   
    var disabled_pri = 'n-check-checkbox';
    var enabled_pri = 'n-check-checkbox n-check-checkbox_checked';


    beforeEach(function() {
        browser.get(my_url);
    });

    it('schould be chosen',function(){
        main_checkbox.click(); 

        checkbox_list.filter(function(elem, index) {
            return elem.getAttribute('class').then(function(text) {
                return text != 'n-check-checkbox n-check-checkbox_disabled' & text!='n-check-checkbox n-check-checkbox_disabled n-check-checkbox_checked';
            });
        }).then(function(filteredElements) {
            filteredElements.each(function(element, index) {
                expect(element.getAttribute('class')).toEqual(disabled_pri); 
            });
        });
    });
}); 

It isn't working. But then I try to use filtering without cycle .each it is working fine.

 describe('Test_3', function() {
    var my_url = 'http://wks-15103:8010/ps/ng-components/examples/ps-checkbox.html'
    var main_checkbox = element(by.xpath("//div[@ng-model='My_Group']/div[1]/span/span[1]"));
    var checkbox_list = element.all(by.xpath("//div[@ng-model='My_Group']/div[2]/div/span/span[1]"));  //это список самих чекбоксов
    var title_checkbox_list = element.all(by.xpath("//div[@ng-model='My_Group']/div[2]/div/span"));  //это список чекбоксов с названиями  
    var disabled_pri = 'n-check-checkbox';
    var enabled_pri = 'n-check-checkbox n-check-checkbox_checked';

    beforeEach(function() {
        browser.get(my_url);
    });

    it('schould be chosen',function(){
        main_checkbox.click();     //Убрали флажок с группового чекбокса   

        checkbox_list.filter(function(elem, index) {
        return elem.getAttribute('class').then(function(text) {
            return text != 'n-check-checkbox n-check-checkbox_disabled' & text!='n-check-checkbox n-check-checkbox_disabled n-check-checkbox_checked';
        });
        }).then(function(filteredElements) {
            filteredElements[0].click();
            filteredElements[0].click();
            expect(filteredElements[0].getAttribute('class')).toEqual(disabled_pri);
        }); 
    }); 
}); 

What is my mistake?