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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 _extract_total_number_of_chars(self):
 """ sets `self.number_chars` to the number of characters as string. """

        self._get_gene_codes_and_seq_lengths()

        sum = 0
        for seq_length in self._gene_codes_and_lengths.values():
            sum += sorted(seq_length, reverse=True)[0]
        self.number_chars = str(sum)