def write_tweets(keyword, file):
    #If the file exists, then read the existing data from the CSV file.
    if os.path.exists(file):
        df = pd.read_csv(file, header=0)
    else:
        df = pd.DataFrame(columns=COLS)
    #page attribute in tweepy.cursor and iteration
    for page in tweepy.Cursor(api.search, q=keyword,
                              count=200, include_rts=False)