input: Write a function to create a virtual assistant using Python and Dialogflow to answer a basic set of questions. The function should continuously take user input and return responses from Dialogflow until the program is terminated. If the user input is empty, the function should print a default message.
  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 not text:
     print('Assistant: Please enter a valid question.')
     continue
    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 virtual_assistant()==None
  assert virtual_assistant()==None
  assert virtual_assistant()==None
  assert virtual_assistant()==None
output: def virtual_assistant():
   while True:
    text = input('User: ')
    if not text:
     print('Assistant: Please enter a valid question.')
     continue
    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)