TopLevelCS root = (TopLevelCS) resource.getContents().get(0);
RelationModel rm = (RelationModel) root.getPivot();

Set<RelationalTransformation> transformations = new HashSet<>();
for (TransformationCS transfCS : root.getOwnedTransformations()) {
    transformations.add((RelationalTransformation) transfCS.getPivot());
}

// Perform some changes inside transformations...
performSomeChanges(rm, transformations);

// What I want to do:
for (RelationalTransformation transformation : transformations) {
    TransformationCS transfCS = transformation.getCS(); // ?
}