<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def delete_cookie(self, key, path='/', domain=None):
 """Delete a cookie. Fails silently if key doesn't exist. :param key: the key (name) of the cookie to be deleted. :param path: if the cookie that should be deleted was limited to a path, the path has to be defined here. :param domain: if the cookie that should be deleted was limited to a domain, that domain has to be defined here. """

        self.set_cookie(key, expires=0, max_age=0, path=path, domain=domain)