Create a DataFrame $\text{'}$df$4\text{'}$ directly using a list of dictionaries. Each dictionary represents a row, with 'city' and 'data' as keys.

def test$\_$exercise$04($self$)$:

df$4=$ exercise$04()$

self.assertTrue$($set$($df$4.$columns$)==\{"$city$",$ "data"$\})$

self.assertEqual$($len$($df$4),3)$