如何检查所有特定文件类型的文件都被复制到一个目录中？

import os
import shutil

def copy_files(source_dir, target_dir, file_extension):
    for root, dirs, files in os.walk(source_dir):
        for file in files:
            if file.endswith(file_extension):
                source_file = os.path.join(root, file)
                target_file = os.path.join(target_dir, file)
                shutil.copy2(source_file, target_file)
                print(f"File {source_file} copied to {target_file}")

source_directory = "/path/to/source/directory"
target_directory = "/path/to/target/directory"
file_extension = ".txt"

copy_files(source_directory, target_directory, file_extension)