protected Object getEdgeProperty(String propName, Edge e) {
		ObjectAttribute<Edge> attrib = getEdgeAttribute(propName);
		Object o = attrib.getValue(e);

		return o;
	}
This is a helper method that gets a property named propName to
from edge e.

@param propName the property name
@param e the edge 
@return the attribute for the indicated edge
Ghidra/Framework/Generic/src/main/java/ghidra/util/graph/DirectedGraph.java