new_contents: import re
  from mitmproxy import ctx
  
  
  def websocket_message(flow):
      # get the latest message
      message = flow.messages[-1]
  
      # simply print the content of the message
      ctx.log.info(message.content)
  
      # manipulate the message content
      message.content = re.sub(r'^Hello', 'HAPPY', message.content)
  
subject: add websocket example