def AddComment(self, comment):
    """Adds a comment to the event tag.

    Args:
      comment (str): comment.
    """
    if not comment:
      return

    if not self.comment:
      self.comment = comment
    else:
      self.comment = ''.join([self.comment, comment])
Adds a comment to the event tag.

    Args:
      comment (str): comment.