code: def _extract_symbols(self, symbols, default=None):
          
          to_ret = {}
          for symbol in symbols:
              symbolInfo = self.elf.symbol_decoder.get_symbol_for_name(symbol)
              if symbolInfo is None:
                  if default is not None:
                      to_ret[symbol] = default
                      continue
                  raise FlashAlgoException("Missing symbol %s" % symbol)
              to_ret[symbol] = symbolInfo.address
          return to_ret
docs: ! @brief Fill 'symbols' field with required flash algo symbols