get_mailinglist Attribute Error

I get an error when using get_mailinglist function. To reproduce run

import ethz_iam_webservice
e = ethz_iam_webservice.login(IAM_USERNAME, IAM_PASSWORD)
ml = e.get_mailinglist('sis@id.ethz.ch')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/beyerleu/.conda/envs/iam/lib/python3.10/site-packages/ethz_iam_webservice/ethz_iam.py", line 128, in get_mailinglist
    data = self.get_request(endpoint, hostname=self.hostname_new)
AttributeError: 'ETH_IAM' object has no attribute 'hostname_new'