function getId( id )
    if not mw.wikibase then
           return "wikibase module not found"
    end
 
    if id then return id end
 
    entity = mw.wikibase.getEntityObject()
    if not entity then return nil end
    return entity.id
end

-- Returns the local page of the data item provided.
function p.page(frame)
    id = getId(frame.args[1])
    if id == nil then
           return "(no element found)"
    end
    return mw.wikibase.sitelink( id )
end