         }
         
         // [3,] -> [3,3]
-        var pb: (Tensor<Float>) -> Tensor<Float> = pullback(at: [99, 33, 55]) { x in
+        let pb: (Tensor<Float>) -> Tensor<Float> = pullback(at: [99, 33, 55]) { x in
             foo(tensor: x, shape: [3, 3])
         }
         

        }
    
        // [3,1] -> [3x3]
        var pb: (Tensor<Float>) -> Tensor<Float> = pullback(at: [[99, 33, 55]]) { x in
            foo(tensor: x, shape: [3, 3])
        }
        

            [1, 2, 3],
            [1, 2, 3],
            [1, 2, 3]]
        let pb: (Tensor<Float>) -> Tensor<Float> = pullback(at: atTensor) { x in
            foo(tensor: x, shape: [1, 3])
        }
        
