What is the white and blue vac line for? 1982 300d w123

[europower]

I am trying to restore order in this 82 300d w123,found this loose line and i dont know what its for, its white with blue,coming from the firewall.

[Fattyman]

Yellow lines are for the locking pods, doors, trunk, fuel. Green is for climate control. Brown is for engine shutoff, purple is for headlight adjusters, Blue is for the seat locks on Coupes (300CD's) so I don't know how they ended up in your 300D. If everything is working just leave it alone!