import functools


def to_Mbit(fn):
    """
    Decorator: convert bit to Mbit in download and upload columns.
    """
    @functools.wraps(fn)
    def wrapper(*args, **kwargs):
        df = fn(*args, **kwargs)
        df["Download"] = [f / 10 ** 6 for f in df["Download"]]
        df["Upload"] = [f / 10 ** 6 for f in df["Upload"]]
        return df

    return wrapper