input: Write a function named `create_virtual_assistant` that sets up a virtual assistant using Python and Dialogflow to answer a basic set of questions. The function should prompt the user for input, send the input to Dialogflow for processing, and print the response from the assistant. Use the Dialogflow API to handle the interactions.
  assert create_virtual_assistant() # Function call with no inputs required as it sets up the assistant
  # The function should internally prompt the user and handle the interaction, so no specific output in assert statements
output: def create_virtual_assistant():
      import dialogflow
      from google.cloud import dialogflow_v2 as dialogflow
      from google.oauth2 import service_account
  
      credentials = service_account.Credentials.from_service_account_file('path_to_your_service_account_file.json')
      session_client = dialogflow.SessionsClient(credentials=credentials)
      session = session_client.session_path('your-project-id', 'unique-session-id')
  
      while True:
          user_input = input("You: ")
          if user_input.lower() in ['exit', 'quit']:
              break
  
          text_input = dialogflow.types.TextInput(text=user_input, language_code='en')
          query_input = dialogflow.types.QueryInput(text=text_input)
  
          response = session_client.detect_intent(session=session, query_input=query_input)
  
          print(f"Assistant: {response.query_result.fulfillment_text}")