input: Write a function to implement a simple chatbot using Python and Dialogflow that can answer questions about the current days of the week. The function should take a session_id and text as inputs and return the fulfillment text from Dialogflow. If session_id is not present, create a new session_id.
  def chatbot_days_of_week(session_id, text):
      if not session_id:
          session_id = create_session_id()
      request = detect_intent_texts(session_id, text)
      response = request.fulfillment_text
      return response
  
  assert chatbot_days_of_week(None, "What's the current day of the week?")=='Wednesday'
  assert chatbot_days_of_week("session123", "What day is it today?")=='Friday'
  assert chatbot_days_of_week("session123", "Can you tell me the day today?")=='Saturday'
  assert chatbot_days_of_week(None, "Is today Monday?")=='No, today is not Monday.'
  assert chatbot_days_of_week("session456", "Which day of the week are we in?")=='Sunday'
output: def chatbot_days_of_week(session_id, text):
      if not session_id:
          session_id = create_session_id()
      request = detect_intent_texts(session_id, text)
      response = request.fulfillment_text
      return response