input: Write a function to create an instance of the "sru" class and call its "search" method, passing in a query string and optionally a collection name, start record number, maximum number of records to return, and record schema. The method should return a "response" object containing the results of the search.
  
  assert search_sru("query string", "collection name", 1, 10, "record schema") != None
  assert search_sru("another query", None, 1, 5) != None
  assert search_sru("empty query", "", 1, 0, None) == False
  assert search_sru("unknown collection", "invalid_collection") == "Exception: Unknown collection"
output: def search_sru(query, collection=None, start=1, max_records=10, schema=None):
      try:
          sru_instance = sru()
          response = sru_instance.search(query, collection, start, max_records, schema)
          return response
      except Exception as e:
          if "Unknown collection" in str(e):
              return "Exception: Unknown collection"
          return False