input: Write a function to create a simple chatbot using Python and Dialogflow that can answer questions about the current days of the week. The function should handle both GET and POST requests, check for the presence of a session ID, and use Dialogflow to detect the intent of the text input before returning a response. If no session ID is present, the function should create one.
  
  assert detect_intent_text("What day is it today?")== "Today is Monday."
  assert detect_intent_text("Is tomorrow Thursday?")== "No, tomorrow is Tuesday."
  assert detect_intent_text("Which days are the weekend?")== "The weekend days are Saturday and Sunday."
  assert detect_intent_text(None)== "No input provided."
output: def detect_intent_text(text):
      if text is None:
          return "No input provided."
      
      session_id = "unique_session_id"
      project_id = "your_project_id"
      language_code = "en"
      
      import dialogflow_v2 as dialogflow
      session_client = dialogflow.SessionsClient()
      session = session_client.session_path(project_id, session_id)
      
      text_input = dialogflow.types.TextInput(text=text, language_code=language_code)
      query_input = dialogflow.types.QueryInput(text=text_input)
      
      response = session_client.detect_intent(session=session, query_input=query_input)
      return response.query_result.fulfillment_text