protected Boolean isLocalInstanceOverridable(String localName) {
        Boolean valueInThis = super.isLocalInstanceOverridable(localName);
        if (valueInThis != null) return valueInThis;
        return backingProfile.isLocalInstanceOverridable(localName);
    }
Creates an overridable profile from the given backing profile. The backing profile will never be
written to.

@param backingProfile the backing profile, which is assumed read only, never null
container-search/src/main/java/com/yahoo/search/query/profile/BackedOverridableQueryProfile.java