input: Write a python function to get the performance score of a website using Google PageSpeed Insights API.
  assert get_website_score('https://www.example.com')==85  # replace with actual expected score
  assert get_website_score('https://www.google.com')==95  # replace with actual expected score
  assert get_website_score('https://www.nonexistentwebsite.com')=='unable to get website score'
output: import requests
  
  def get_website_score(url):
      api_key = 'YOUR_API_KEY'  # Replace with your actual Google PageSpeed Insights API key
      api_url = f'https://www.googleapis.com/pagespeedonline/v5/runPagespeed?url={url}&key={api_key}'
      
      try:
          response = requests.get(api_url)
          response.raise_for_status()
          data = response.json()
          score = data['lighthouseResult']['categories']['performance']['score'] * 100
          return int(score)
      except (requests.exceptions.RequestException, KeyError):
          return 'unable to get website score'