docs: def primary_from_id(self, tax_id):
          """
          Returns primary taxonomic name associated with tax_id
          """
          s = select([self.names.c.tax_name],
                     and_(self.names.c.tax_id == tax_id,
                          self.names.c.is_primary))
          res = s.execute()
          output = res.fetchone()
  
          if not output:
              msg = 'value "{}" not found in names.tax_id'.format(tax_id)
              raise ValueError(msg)
          else:
              return output[0]