message: Fixed bad English
diff: @@ -98,7 +98,7 @@ std::vector<ObservedWorld> World::Observe(const std::vector<AgentId>& agent_ids)
  std::vector<ObservedWorld> observed_worlds;
  for (auto agent_id : agent_ids) {
  if(agents_.find(agent_id) == agents_.end()) {
  - std::cout << "Unvalid agent id " << agent_id << ". Skipping ...." << std::endl;
  + std::cout << "Invalid agent id " << agent_id << ". Skipping ...." << std::endl;
  continue;
  }
  ObservedWorld observed_world(*current_world_state,
  