input: 
  def sru_search(query: str, collection: str = None, startrecord: int = 1, maximumrecords: int = 1, recordschema: str = None) -> response:
      """
      Searches the KB SRU database using the provided query and optional parameters.
      Returns a response object containing the search results.
      
      >>> sru_search('Python', 'GGC')
      <__main__.response object at 0x...>
      >>> sru_search('ISBN:9781491901541', 'GGC').identifiersISBN
      ['9781491901541']
      """
  
output:     import requests
      from xml.etree import ElementTree as ET
  
      base_url = "http://z3950.loc.gov:7090/voyager"
      params = {
          'version': '1.1',
          'operation': 'searchRetrieve',
          'query': query,
          'startRecord': startrecord,
          'maximumRecords': maximumrecords,
          'recordSchema': recordschema if recordschema else 'marcxml'
      }
  
      if collection:
          params['x-collection'] = collection
  
      response = requests.get(base_url, params=params)
      response_xml = response.content
      root = ET.fromstring(response_xml)
  
      class Response:
          def __init__(self, root):
              self.root = root
              self.records = []
              self.identifiersISBN = []
              self.parse_records()
  
          def parse_records(self):
              for record in self.root.findall('.//{http://www.loc.gov/MARC21/slim}record'):
                  self.records.append(record)
                  isbn = record.find('.//{http://www.loc.gov/MARC21/slim}datafield[@tag="020"]/{http://www.loc.gov/MARC21/slim}subfield[@code="a"]')
                  if isbn is not None:
                      self.identifiersISBN.append(isbn.text)
  
      return Response(root)