In a medium size bowl, beat the cake mix, eggs, and butter until smooth. If using, add the chocolate chips and mix just until the chips are well incorporated throughout the batter. Pour the batter into prepared baking pan. Spread the pie filling on top of the cake batter (do not stir or attempt to mix together the cake batter and pie filling; they will blend naturally during the baking process). Sprinkle the top with the chopped nuts.