argumentsOfInterestFor method
Return the arguments that we care about for the select. In this case they will all be passed in as a Map rather than as the named arguments used in Plural/Gender.
Implementation
Map argumentsOfInterestFor(MethodInvocation node) {
SetOrMapLiteral casesArgument =
node.argumentList.arguments[1] as SetOrMapLiteral;
return new Map.fromIterable(casesArgument.elements,
key: (node) => _keyForm(node.key), value: (node) => node.value);
}