Explain "import os
import shutil

# Copy contents of sorter-chunks directory to cured-chunks directory
shutil.copytree('./sorter-chunks/', './cured-chunks/')

# Define a function to delete files and handle undo
def delete_file(file_path):
    # Store original file contents in case of undo
    with open(file_path, 'r') as f:
        original_content = f.read()
    # Prompt user to delete file
    while True:
        response = input(f"Delete {file_path}? (y/n/u/s): ")
        if response == 'y':
            os.remove(file_path)
            print(f"{file_path} deleted.")
            break
        elif response == 'n':
            print(f"{file_path} not deleted.")
            break
        elif response == 'u':
            # Undo delete by restoring original file contents
            with open(file_path, 'w') as f:
                f.write(original_content)
            print(f"{file_path} delete undone.")
            # Return to previous file
            return True
        elif response == 's':
            print("Saving progress and quitting program.")
            # Save progress and exit program
            save_progress(current_dir, i)
            return False
        else:
            print("Invalid response. Please enter 'y', 'n', 'u', or 's'.")
    return False

# Define a function to save the current directory and file index
def save_progress(current_dir, i):
    with open('./saved_progress.txt', 'w') as f:
        f.write(f"{current_dir}\n{i}")

# Check for saved progress file and resume where left off
if  Provide the entire answer in JSON format.
user