input: Write a function to get a response from a Dialogflow session using the provided session client.
  assert get_response("Hello, how are you?") != ""
  assert get_response("What is the weather today?") != ""
  assert get_response("Tell me a joke.") != ""
output: def get_response(query_text):
      from google.cloud import dialogflow_v2 as dialogflow
      import os
  
      os.environ["GOOGLE_APPLICATION_CREDENTIALS"] = "path/to/your/service-account-file.json"
  
      project_id = "your-project-id"
      session_id = "unique-session-id"
      language_code = "en"
  
      session_client = dialogflow.SessionsClient()
      session = session_client.session_path(project_id, session_id)
  
      text_input = dialogflow.TextInput(text=query_text, language_code=language_code)
      query_input = dialogflow.QueryInput(text=text_input)
  
      response = session_client.detect_intent(request={"session": session, "query_input": query_input})
  
      return response.query_result.fulfillment_text