private Collection<ComponentSpecification> spaceSeparatedComponentSpecificationsFromAttribute(Element spec, String attributeName) {
        return toComponentSpecifications(XmlHelper.spaceSeparatedSymbolsFromAttribute(spec, attributeName));
    }
Build an Inheritance object from an inheritance section.
@author Tony Vaagenes
config-model/src/main/java/com/yahoo/vespa/model/builder/xml/dom/chains/InheritanceBuilder.java