Authenticate with the server.

        :param username: The username of an existing user
        :param password: The password for the user
        :return: The authentication response from the REST endpoint

def login(self, username, password):
        """
        Authenticate with the server.

        :param username: The username of an existing user
        :param password: The password for the user
        :return: The authentication response from the REST endpoint
        """

        data = self._authenticate(
            grant_type='password',
            username=username,
            password=password,
            client_id=self._client_id,
            client_secret=self._client_secret
        )

        self._username = username
        self._password = password

        return data