input: Write a function to create an instance of the "sru" class and perform a search using its "search" method. The function should accept a query string, an optional collection name, a start record number, a maximum number of records to return, and a record schema. The function should return the "response" object containing the search results. Provide assert test cases to verify the function behavior.
  
  assert search_kb_sru("test query", "DPO", 1, 10, "ddd").nr_of_records > 0
  assert search_kb_sru("test query", "GGC", 1, 5, "dcx").nr_of_records > 0
  assert search_kb_sru("test query", "ANP", 2, 3, "dcx").nr_of_records > 0
  assert search_kb_sru("invalid query", "BYVANCK", 1, 1, "dcx").nr_of_records == 0
  assert search_kb_sru("test query", "SGD", 1, 1, "dcx").nr_of_records > 0
output: def search_kb_sru(query, collection=None, start_record=1, max_records=10, record_schema="dcx"):
      sru_instance = sru()
      response = sru_instance.search(query, collection, start_record, max_records, record_schema)
      return response