我怎么才能得到最大的20个单词的频率？

import re
from collections import Counter
import heapq

def get_top_n_words(text, n=20):
    # 使用正则表达式移除标点符号并将文本转换为小写
    words = re.findall(r'\w+', text.lower())
    
    # 计算每个单词的出现频率
    word_counts = Counter(words)
    
    # 获取出现频率最高的n个单词
    top_n_words = heapq.nlargest(n, word_counts.items(), key=lambda item: item[1])
    
    return top_n_words

# 示例文本
text = """
Your large text goes here. This is an example text to demonstrate the function.
"""

# 获取频率最高的20个单词
top_20_words = get_top_n_words(text)

# 打印结果
for word, frequency in top_20_words:
    print(f"{word}: {frequency}")