Shouldn't the boss and his colleagues know about going out to travel units for leave?

That's not true. When traveling or taking time off from work, you should indicate the reasons on the note.

Report to the unit leader when going out of the city or going abroad. As for my colleagues, I want to do something.

Needless to say, low-key ones, good relationships can also be said, bring some souvenirs.

Come back, or ask colleagues if they want to bring back what they need.