def METHOD_NAME(rows):
    if not rows:
        return [], ""
    for r in rows:
        if isinstance(r, str):
            continue
        if not isinstance(r, dict):
            return False, "A row must be a dictionary or a string"
        cap_cols = r.get("COLUMNS")
        if cap_cols:
            r["columns"] = r.pop("COLUMNS")
    return True, ""