input: def get_recent_tweets(username: str) -> str:
      """Get the most recent tweets from a specified Twitter user.
      
      >>> get_recent_tweets("@elonmusk")
      'Text of recent tweets from @elonmusk.'
      """
output:     import requests
      url = f"https://api.twitter.com/2/users/by/username/{username.strip('@')}/tweets"
      headers = {
          "Authorization": "Bearer YOUR_BEARER_TOKEN"
      }
      response = requests.get(url, headers=headers)
      if response.status_code == 200:
          tweets = response.json().get("data", [])
          recent_tweets = [tweet["text"] for tweet in tweets]
          return " ".join(recent_tweets)
      else:
          return "Failed to retrieve tweets."