def top_ten(df,col_na):
    """ Presenting the top ten conutries in the dataframe
    This function accepts the dataframe and column name
    
    keyword arguments 
    df - dataframe of country names and medals
    col_na  - column name is country_name and medals
    
    returns  - top 10 country list

    """
    country_list = []
    
    a = df.nlargest(10,col_na)
    country_list = list(a['Country_Name'])
    return country_list