input: Write a python function to scrape the price of iPhone 11 from Apple's website using BeautifulSoup.
  assert scrape_iphone_price('https://store.apple.com/us/buy-iphone/iphone-11') != ''
  assert isinstance(scrape_iphone_price('https://store.apple.com/us/buy-iphone/iphone-11'), str)
  assert scrape_iphone_price('https://store.apple.com/us/buy-iphone/iphone-11').startswith('$')
output: import requests
  from bs4 import BeautifulSoup
  
  def scrape_iphone_price(url):
      response = requests.get(url)
      soup = BeautifulSoup(response.content, 'html.parser')
      
      price_tag = soup.find('span', {'class': 'current_price'})
      if price_tag:
          return price_tag.text.strip()
      return ''