'Access the credential_lists
:returns: twilio.rest.api.v2010.account.sip.credential_list.CredentialListList
:rtype: twilio.rest.api.v2010.account.sip.credential_list.CredentialListList'

@property
def credential_lists(self):

    if (self._credential_lists is None):
        self._credential_lists = CredentialListList(self._version, account_sid=self._solution['account_sid'])
    return self._credential_lists
