input: Write a function to create an instance of the "sru" class and perform a search using the "search" method, passing appropriate default values for the parameters. The function should return the search results in the form of a "response" object, which can be used to extract specific information such as titles, creators, and subjects.
  sru_instance = sru()
  response_obj = sru_instance.search("query string", "collection", 1, 10, "record schema")
  assert response_obj.titles == [expected titles list]
  assert response_obj.creators == [expected creators list]
  assert response_obj.subjects['Brinkman'] == [expected subjects Brinkman list]
output: def perform_search():
      sru_instance = sru()
      response_obj = sru_instance.search("query string", "collection", 1, 10, "record schema")
      return response_obj