[Plugin: Contact Form 7] How to set value for "wpcf7_form_action_url" filter?

In a different post, almost a year ago, Takayuki Miyoshi has said that “wpcf7_form_action_url” is a filter hook for Contact Form 7. You can make a plugin which can change the value of action= attribute of a form with that filter.

I want to change the value of action= attribute of a form with the “wpcf7_form_action_url” filter but I don’t know how to achieve this. Can anyone give me some insights?