input: Write a python function to scrape a webpage and extract its title, keywords, description, and all URLs. Use the requests and BeautifulSoup libraries. 
  assert scrape_webpage('www.example.com') == {'title': 'Example Domain', 'keywords': ['example', 'domain'], 'description': ['This domain is for use in illustrative examples in documents.'], 'urls': ['http://www.iana.org/domains/example']}
  assert scrape_webpage('www.anotherexample.com') == {'title': 'Another Example Domain', 'keywords': ['another', 'example'], 'description': ['This is another example domain.'], 'urls': ['http://www.iana.org/domains/another-example']}
output: def scrape_webpage(url):
      import requests
      from bs4 import BeautifulSoup
  
      response = requests.get(f'http://{url}')
      soup = BeautifulSoup(response.text, 'html.parser')
  
      title = soup.title.string if soup.title else ''
      
      keywords_meta = soup.find('meta', attrs={'name': 'keywords'})
      keywords = keywords_meta['content'].split(',') if keywords_meta else []
      
      description_meta = soup.find('meta', attrs={'name': 'description'})
      description = [description_meta['content']] if description_meta else []
      
      urls = [a['href'] for a in soup.find_all('a', href=True)]
      
      return {
          'title': title,
          'keywords': keywords,
          'description': description,
          'urls': urls
      }