Ensure that an output port is mapped to only once
Ensure that an output port is mapped to only once

linus-sherrill/sprokit,linus-sherrill/sprokit,mathstuf/sprokit,mathstuf/sprokit,linus-sherrill/sprokit,Kitware/sprokit,linus-sherrill/sprokit,mathstuf/sprokit,Kitware/sprokit,Kitware/sprokit,mathstuf/sprokit,Kitware/sprokit