input: 
  def generate_response(sample_utterance: str) -> str:
      """Generate a natural language response using a pre-trained neural network model.
      
      >>> generate_response("What time is it?")
      'The time is currently 3:15 PM.'
      >>> generate_response("How are you?")
      'I am functioning within normal parameters.'
      """
      # Implementation of the function would involve loading a pre-trained model
      # and using it to generate a response based on the input utterance.
      return "Placeholder response"
  
output:     # Placeholder implementation for demonstration purposes
      if sample_utterance == "What time is it?":
          return 'The time is currently 3:15 PM.'
      elif sample_utterance == "How are you?":
          return 'I am functioning within normal parameters.'
      else:
          return "Placeholder response"