# Find derivative of a network with NetPortGradient?

GROUPS:
 There's a function NetPortGradient, but I can't figure out how it works.To give a specific example (with poetic license of the notation), consider the image x = ExampleData[{"TestImage","Flower"}] The probability [x] in the ImageIdentify network is 0.182434Then a Newton quotient can be defined: y[[row, column, channel]] = Limit[h -> 0, ([ReplacePart[x,{row, column, channel} -> x[[row, column, channel]] + h]] - 0.182434) / h] That is, the functional derivative of the identification probability with respect to each pixel.How can this image be found?