def add_extra_headers(self, sample_names):
        """
        If there are samples, add any additional keys they might use
        to supplement the default headers.
        Return the headers headers for adding, with the format:
        [(header_name, header_display_name), ....]
        """
        if not sample_names:
            return []
        full_headers = list(self.orient_data[sample_names[0]].keys())
        add_ons = []
        for head in full_headers:
            if head not in self.header_names:
                add_ons.append((head, head))
        return add_ons