def METHOD_NAME(self, rd: RadarData, operation: str, k: int):
    assert not rd.compressed, "Passed RadarData instance is compressed"
    data = rd.data
    indices = self.indices[f"{k}_nearest"]
    values = np.take(data.T, indices)
    if operation == "":
        return values
    elif operation == "mean":
        return np.nanmean(values, axis=1).reshape(-1, 1)
    elif operation == "std":
        return np.nanstd(values, axis=1).reshape(-1, 1)
    else:
        raise Exception(f"{operation} operation not implemented yet.")