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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _authenticate(self):
 """Authenticate with netcup server. Must be called first."""

        login_info = self._apicall('login')
        self.api_session_id = login_info['apisessionid']
        if not self.api_session_id:
            raise Exception('Login failed')
        # query ttl and verify access to self.domain:
        zone_info = self._apicall('infoDnsZone', domainname=self.domain)
        self.zone_ttl = zone_info['ttl']