https://stackoverflow.com/questions/20790932/what-is-the-logic-behind-the-using-keyword-in-c
for https://github.com/mavlink/mavros/blob/master/mavros/include/mavros/mavros_uas.h#L66
https://msdn.microsoft.com/ko-kr/library/dd293608.aspx
for https://github.com/mavlink/mavros/blob/master/mavros/src/lib/mavros.cpp#L134
https://msdn.microsoft.com/ko-kr/library/dn956974.aspx
for
