docs: public List<ECKey> getPubKeys() {
          if (!ScriptPattern.isSentToMultisig(this))
              throw new ScriptException(ScriptError.SCRIPT_ERR_UNKNOWN_ERROR, "Only usable for multisig scripts.");
  
          ArrayList<ECKey> result = Lists.newArrayList();
          int numKeys = Script.decodeFromOpN(chunks.get(chunks.size() - 2).opcode);
          for (int i = 0 ; i < numKeys ; i++)
              result.add(ECKey.fromPublicOnly(chunks.get(1 + i).data));
          return result;
      }