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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_slide_footer(self, slide_no):
 """Add the slide footer to the output if enabled."""


        if self.builder.config.slide_footer:
            self.body.append(
                '\n<div class="slide-footer">%s</div>\n' % (
                    self.builder.config.slide_footer,
                ),
            )