what will be the code if I want to enter the default username and password in login details…how I can make function so that it can call itself I don’t want to use sendKeys"abc"
That sounds like a very exact sort of flow. Appium doesn’t write your tests for you; it only gives you tools to write your tests for yourself.
Typing must be performed through sendKeys or setValue. You’ll have to make some sort of call eventually to send your username and password (you’re using a dummy account, right?)