input: 
  def feature_extraction(input_str: str) -> dict:
      """Extract features from a given JSON string.
      >>> feature_extraction('{"id":111,"title":"This is a sample title","body":"This is a sample body text"}')
      {'id': 111, 'title': 'This is a sample title', 'body_len': 30}
      """
      import json
      data = json.loads(input_str)
  
      features = {
          "id": data["id"],
          "title": data["title"],
          "body_len": len(data["body"])
      }
  
      return features
  
output:     import json
      data = json.loads(input_str)
  
      features = {
          "id": data["id"],
          "title": data["title"],
          "body_len": len(data["body"])
      }
  
      return features