I am trying to fill a custom shaped node but as can be observed in the example below the fill does not occur naturally rather it uses its default shape to fill. Any insights?
\documentclass[letterpaper]{article}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric,calc}
\setlength{\parindent}{0pt}
\begin{document}
\begin{tikzpicture}
\draw (0,0) -- (\textwidth-0.4pt, 0) node[
fill=blue!20,
append after command={[rounded corners=0pt](b.west)|-(b.north)},
append after command={[rounded corners=0pt](b.north)-|(b.east)},
append after command={[rounded corners=1pt](b.east)|-(b.south)},
append after command={[rounded corners=5pt](b.south)-|(b.west)},
anchor=north west,
at start,
text=white]
(b) {Example} ;
\end{tikzpicture}
\end{document}

