prettyPrint method
Uses a rough approximation of reverse polish notation to render the parsed value of a FHIRPath in a more human readable way than verbosePrint, while still demonstrating how the expression was parsed and nested according to this package
Implementation
@override
String prettyPrint([int indent = 2]) =>
'${" " * (indent - 1)}+${after.prettyPrint(indent + 1)}';