How to override record-edit-form's methods

Similar to aura component's recordEditForm, lightning web component's record-edit form has predefined methods which can be override. These methods are

1. onload

2. onsubmit

3. onsuccess

4. onerror

for all of these methods you can provide your own handlers. These are useful for handling errors, showing success message, modify fields values before submitting the form and storing the records values in variables etc.

Let me know if you face any problem in implementing this.