Python function not callable from tavern script for saving

[ShreyanshAyanger-Nykaa]

Hi, I am calling a save function after getting response from my api, now in the response received i need to format string and save only few elements present,
response: status_code: 200 save: headers: res_key: $ext: function: testing_utils:extract_sessid extra_kwargs: head: headers
however, my tavern yaml is unable to call extract_string method in testing_utils file,
But other functions written in testing_utils are working fine with following syntax
verify_response_with: - function: testing_utils:check_jsonpath_value

Please help, basically in above way mentioned, the testing_utils file is not accessible ( inside save function) but in same tavern script existing test cases are able to access the same ( with verify_response_with).