applyUsageHint function
Implementation
String applyUsageHint(String content) {
var lines = LineSplitter.split(content).toList();
var contentUsesMacros = lines.any((line) => line.isAnyMacro());
if (contentUsesMacros && lines.first != usageHint) {
return [usageHint, ...lines].join('\n');
}
return content;
}