def encode_bookingid(df):
    """
        Bookingid flag one-hot encoder.
        inputs:
            df: Dataframe which have Bookingid column (pandas df series)
        return:
            df: Dataframe which have only Bookingid indicator [0/1] (pandas df series)
    """
    indx = df['bookingid'].isna()
    df.loc[indx, 'bookingid'] = 0
    df.loc[~indx, 'bookingid'] = 1
    return df
