docs: def convert_blocks_to_string(self):
          """
          New method, only in MegaDatasetBlock class.
  
          :return: flattened data blocks as string
          """
          taxa_ids = [[]] * int(self.data.number_taxa)
          sequences = [''] * int(self.data.number_taxa)
  
          for block in self._blocks:
              for index, seq_record in enumerate(block):
                  taxa_ids[index] = '{0}_{1}_{2}'.format(seq_record.voucher_code,
                                                         seq_record.taxonomy['genus'],
                                                         seq_record.taxonomy['species'],
                                                         )
                  sequence = get_seq(seq_record, self.codon_positions,
                                     aminoacids=self.aminoacids,
                                     degenerate=self.degenerate)
                  sequences[index] += sequence.seq
                  if sequence.warning:
                      self.warnings.append(sequence.warning)
  
          out = ''
          for index, value in enumerate(taxa_ids):
              out += '#{0}\n{1}\n'.format(taxa_ids[index], sequences[index])
          return out