//////////////////////////////////////////////////
void TopicManager::clearAdvertisedTopics(){
  this->advertisedTopics.clear();
}

mkdir build
cd build
make 

1. gzserver
2. <path-to-repo>/build/request_publisher "(-10,10)(10,10)(10,-10)(-10,-10)" 10 0.01 ~/map.png
3. <path-to-repo>/build/request_subscriber

request_publisher: /usr/include/boost/smart_ptr/shared_ptr.hpp:734: typename boost::detail::sp_member_access<T>::type boost::shared_ptr<T>::operator->() const [with T = gazebo::transport::Publication; typename boost::detail::sp_member_access<T>::type = gazebo::transport::Publication*]: Assertion `px != 0' failed.