public void validate(DeployLogger logger) {
        for (var inheritedName : inherited) {
            var inheritedSummary = owner.getSummary(inheritedName);
            // TODO: Throw when no one is doing this anymore
            if (inheritedName.equals("default"))
                logger.logApplicationPackage(WARNING, this + " inherits '" + inheritedName +
                                                      "', which makes no sense. Remove this inheritance");
            else if (inheritedSummary == null )
                throw new IllegalArgumentException(this + " inherits '" + inheritedName +
                                                   "', but this is not present in " + owner);
        }
    }
Returns the parent of this, if any
config-model/src/main/java/com/yahoo/vespa/documentmodel/DocumentSummary.java