def METHOD_NAME(v, values):
    if not v:
        if "first_name" in values or "last_name" in values:
            first_name = values.get("first_name") or ""
            last_name = values.get("last_name") or ""
            full_name = f"{first_name} {last_name}" if last_name else first_name
            return full_name
    else:
        return v