如何在Flask服务器上主动删除输入到文本文件中的重复项？

from flask import Flask, render_template, request

app = Flask(__name__)

@app.route('/', methods=['GET', 'POST'])
def index():
    if request.method == 'POST':
        input_text = request.form['input_text']
        unique_text = remove_duplicates(input_text)
        write_to_file(unique_text)
        return '去重后的内容已成功写入文件！'
    return render_template('index.html')

def remove_duplicates(input_text):
    unique_text = list(set(input_text.split()))
    return ' '.join(unique_text)

def write_to_file(text):
    with open('output.txt', 'w') as file:
        file.write(text)

if __name__ == '__main__':
    app.run()