How did the author of Jonah know about this conversation?

In Jonah 4:9 we read a dialog between God and Jonah: > But God said to Jonah, Do you have a right to be angry about the vine? > I do, he said. I am angry enough to die. But the LORD said, You have > been concerned about this vine, though you did not tend it or make it > grow. It sprang up overnight and died overnight. But Nineveh has more > than a hundred and twenty thousand people who cannot tell their right > hand from their left, and many cattle as well. Should I not be > concerned about that great city? How did the author of this passage know the exact conversation?