input: Write a python function to fetch the most common words from a given URL.
  assert fetch_most_common_words('https://en.wikipedia.org/wiki/Genetic_algorithm', 5) == [('the', 70), ('of', 60), ('and', 50), ('in', 40), ('a', 30)]
  assert fetch_most_common_words('https://en.wikipedia.org/wiki/Python_(programming_language)', 3) == [('Python', 100), ('programming', 80), ('language', 60)]
  assert fetch_most_common_words('https://en.wikipedia.org/wiki/Artificial_intelligence', 4) == [('AI', 90), ('intelligence', 70), ('artificial', 50), ('the', 30)]
output: def fetch_most_common_words(url, n):
      import requests
      from collections import Counter
      from bs4 import BeautifulSoup
      import re
  
      # Fetch the content from the URL
      response = requests.get(url)
      soup = BeautifulSoup(response.content, 'html.parser')
  
      # Extract text from the content
      text = soup.get_text()
  
      # Tokenize the text
      words = re.findall(r'\b\w+\b', text.lower())
  
      # Count the frequency of each word
      word_counts = Counter(words)
  
      # Get the most common words
      most_common_words = word_counts.most_common(n)
  
      return most_common_words