How to create double labelled edges in Graphviz? -

i create more 1 label 1 edge. result i'm interested in looks this:

note edge {0,2} has 2 labels: e , z. 1 above edge, other 1 - below. exact outcome want. how can achieve this?

have tried

digraph g {   graph [ splines = false rankdir="lr" ]   -> b [ label = "foo" ];   -> b [ label = "bar" ]; } 

i've checked using http://www.webgraphviz.com/

result looks like

taken stackoverflow question graphviz, grouping same edges