def METHOD_NAME(prev_content, new_content):
    content = {}
    for attr, systems in chain(prev_content.items(), new_content.items()):
        attr = normalize(attr)
        s = content.setdefault(attr, [])
        for system in systems:
            s.append(system)
    # Return with sorted data
    return {
        attr: merge_systems(content[attr])
        for attr in sorted(content.keys())
        if attr not in BLOCKLIST
    }