input: Write a function to create a virtual assistant using Python and Dialogflow to answer a basic set of questions. The function should initialize the Dialogflow session and continuously accept user input, relay it to Dialogflow, and print the assistant's response. If the input is 'exit', the function should terminate the loop and end the session.
  import dialogflow_v2 as dialogflow
  import requests
  
  project_id = 'project-id'
  session_client = dialogflow.SessionsClient()
  session = session_client.session_path(project_id, 'session-id')
  
  def virtual_assistant():
      while True:
          text = input('User: ')
          if text == 'exit':
              break
          text_input = dialogflow.types.TextInput(text=text, language_code='en-US')
          query_input = dialogflow.types.QueryInput(text=text_input)
          response = session_client.detect_intent(session=session, query_input=query_input)
  
          print('Assistant:', response.query_result.fulfillment_text)
  
  assert virtual_assistant()==None
  assert response.query_result.fulfillment_text=='Expected Assistant Response'
output: def virtual_assistant():
      while True:
          text = input('User: ')
          if text == 'exit':
              break
          text_input = dialogflow.types.TextInput(text=text, language_code='en-US')
          query_input = dialogflow.types.QueryInput(text=text_input)
          response = session_client.detect_intent(session=session, query_input=query_input)
  
          print('Assistant:', response.query_result.fulfillment_text)