input: Write a python function to download a file from a given URL and show a progress bar.
  assert download_file('https://example.com/file.txt', 'file.txt') == True
  assert os.path.exists('file.txt') == True
output: def download_file(url, destination):
      import requests
      from tqdm import tqdm
      import os
  
      response = requests.get(url, stream=True)
      total_size = int(response.headers.get('content-length', 0))
      block_size = 1024
      
      progress_bar = tqdm(total=total_size, unit='iB', unit_scale=True)
      
      with open(destination, 'wb') as file:
          for data in response.iter_content(block_size):
              progress_bar.update(len(data))
              file.write(data)
      progress_bar.close()
      
      return os.path.exists(destination)