input: Write a python function to optimize a webpage by converting the title, keywords, and description to lowercase.
  assert "example" in optimize_webpage("http://example.com")
  assert "another example" in optimize_webpage("http://anotherexample.com")
output: import requests
  from bs4 import BeautifulSoup
  
  def optimize_webpage(url):
      response = requests.get(url)
      soup = BeautifulSoup(response.content, 'html.parser')
  
      if soup.title:
          soup.title.string = soup.title.string.lower()
  
      if soup.find("meta", {"name": "keywords"}):
          keywords = soup.find("meta", {"name": "keywords"})
          keywords['content'] = keywords['content'].lower()
  
      if soup.find("meta", {"name": "description"}):
          description = soup.find("meta", {"name": "description"})
          description['content'] = description['content'].lower()
      
      return str(soup)