input: Write a function to create a virtual assistant using Python and Dialogflow to answer a basic set of questions. The function should take user input and return the assistant's response. If the user input is empty, the function should indicate no input received.
  
  
  def virtual_assistant(project_id, session_id):
      import dialogflow_v2 as dialogflow
      session_client = dialogflow.SessionsClient()
      session = session_client.session_path(project_id, session_id)
      
      while True:
          text = input('User: ')
          if not text:
              return "No input received."
          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)
          return response.query_result.fulfillment_text
  
  assert virtual_assistant('project-id', 'session-id') == "No input received."
  assert type(virtual_assistant('project-id', 'session-id')) == str
  
output: def virtual_assistant(project_id, session_id):
      import dialogflow_v2 as dialogflow
      session_client = dialogflow.SessionsClient()
      session = session_client.session_path(project_id, session_id)
      
      while True:
          text = input('User: ')
          if not text:
              return "No input received."
          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)
          return response.query_result.fulfillment_text