def METHOD_NAME(self, tsr):
    if not torch.is_tensor(tsr):
        return "DenseLinearOperator must take a torch.Tensor; got {}".format(tsr.__class__.__name__)
    if tsr.dim() < 2:
        return "DenseLinearOperator expects a matrix (or batches of matrices) - got a Tensor of size {}.".format(
            tsr.shape
        )