code: def authenticate(self, account_name, password):
          
          self.auth_token = self.authenticator.authenticate(self.transport,
                                                            account_name,
                                                            password)
docs: Authenticates zimbra account.
          @param account_name: account email address
          @param password: account password
          @raise AuthException: if authentication fails
          @raise SoapException: if soap communication fails