Improve the efficency of setting collections and add_to_collection().
Improve the efficency of setting collections and add_to_collection().



Former-commit-id: 957810865d16afc9998825afb33b7768a9460132
julie-sullivan/phytomine,julie-sullivan/phytomine,julie-sullivan/phytomine,julie-sullivan/phytomine,julie-sullivan/phytomine,julie-sullivan/phytomine,julie-sullivan/phytomine