I do not understand this error: MethodError: no method matching iterate(::DataFrame)

I thought you needed me to give a shapefile for the MWE. I already have my shapefile in a dataframe.
Anyways I am currently using VegaLite. So I converted my shapefile to a topojson. The conversation is here: https://discourse.julialang.org/t/how-to-make-vegalite-read-my-topojson-file/34546/10