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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _add_comments( self, comments: Optional[Sequence[str]], original_string: str = "" ) -> str: """ Returns a string with comments added if ignore_comments is not set. """

        if self.config['ignore_comments']:
            return self._strip_comments(original_string)[0]

        if not comments:
            return original_string
        else:
            return "{0}{1} {2}".format(self._strip_comments(original_string)[0],
                                       self.config['comment_prefix'],
                                       "; ".join(comments))