input: Write a python function to fetch and return tweets containing a specific hashtag using Tweepy.
  assert fetch_tweets('#100DaysOfCode') is not None
  assert isinstance(fetch_tweets('#Python'), list)
  assert all(isinstance(tweet, str) for tweet in fetch_tweets('#Coding'))
output: def fetch_tweets(hashtag):
      import tweepy
  
      # Assuming you have your own credentials from Twitter Developer Account
      consumer_key = 'YOUR_CONSUMER_KEY'
      consumer_secret = 'YOUR_CONSUMER_SECRET'
      access_token = 'YOUR_ACCESS_TOKEN'
      access_token_secret = 'YOUR_ACCESS_TOKEN_SECRET'
  
      # Authorize the API
      auth = tweepy.OAuth1UserHandler(consumer_key, consumer_secret, access_token, access_token_secret)
      api = tweepy.API(auth)
  
      # Fetch tweets containing the hashtag
      tweets = api.search_tweets(q=hashtag, count=100, lang='en')
  
      # Extract text from tweets
      tweet_texts = [tweet.text for tweet in tweets]
  
      return tweet_texts