Rename TensorProduct and implement TensorCore.tensor

src/kernels/kerneltensorproduct.jl

@@ -1,5 +1,5 @@
 """
-    KernelTensorProduct <: Kernel
+    KernelTensorProduct
 
 Tensor product of kernels.
 
@@ -139,7 +139,6 @@ function printshifted(io::IO, kernel::KernelTensorProduct, shift::Int)
         for _ in 1:(shift + 1)
             print(io, "\t")
         end
-        print(io, "- ")
         printshifted(io, k, shift + 2)
     end
 end

test/kernels/kerneltensorproduct.jl

@@ -14,6 +14,9 @@
     @test kernel1 == kernel2
     @test kernel1.kernels === (k1, k2) === KernelTensorProduct((k1, k2)).kernels
     @test length(kernel1) == length(kernel2) == 2
+    @test string(kernel1) == (
+        "Tensor product of 2 kernels:\n\tSquared Exponential Kernel\n\tExponential Kernel"
+    )
     @test_throws DimensionMismatch kernel1(rand(3), rand(3))
 
     @testset "val" begin