<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_comment(self, post=None, name=None, email=None, pub_date=None, website=None, body=None):
 """ Adds a comment to the post provided. """

        if post is None:
            if not self.posts:
                raise CommandError("Cannot add comments without posts")
            post = self.posts[-1]
        post["comments"].append({
            "user_name": name,
            "user_email": email,
            "submit_date": pub_date,
            "user_url": website,
            "comment": body,
        })