addInitialAssignment[options] adds a InitialAssignment to the current model. Options are the same as InitialAssignmentToSBML.
addInitialAssignment[x, options] is the same as addInitialAssignment[id->x, options].
modifyInitialAssignment[options] modifies a compartment type in the current model. Options are the same as InitialAssignmentToSBML.
modifyInitialAssignment[x, options] is the same as modifyInitialAssignment[id->x, options].
removeInitialAssignment[id] removes a compartment type with the given id from the current model.addInitialAssignment, removeInitialAssignment, modifyInitialAssignment new in 2.5.12.