def METHOD_NAME(self, x, target) -> None:
    """
    Append a point and its target value to the known data.
    Args:
        x (ndarray): A single query point.
        target (float): Target value.
    """
    # if x in self:
    #     raise ValueError("Data point {} is not unique.".format(x))
    # Insert data into unique dictionary.
    x = self.scaler.transform(x)
    self._params = np.concatenate([self._params, x.reshape(1, -1)])
    self._target = np.concatenate([self._target, [target]])