input: 
  def generate_response(question):
      """ Generate a response to a user's query about XYZ company or service.
      If the question is in the predefined answers dictionary, return the corresponding answer.
      Otherwise, return a random response indicating uncertainty.
      >>> generate_response('What is XYZ?')
      'XYZ is a company that provides XYZ services.'
      >>> generate_response('Where is XYZ located?')
      'XYZ is located in ABC city.'
      >>> generate_response('Non-existent question')
      'I am not sure I understand.'
      """
  
output:     predefined_answers = {
          'What is XYZ?': 'XYZ is a company that provides XYZ services.',
          'Where is XYZ located?': 'XYZ is located in ABC city.'
      }
      
      if question in predefined_answers:
          return predefined_answers[question]
      else:
          return 'I am not sure I understand.'