Error: Could not find or load main class FlameGraph

[ennishol]

Usage hints for converter indicate FlameGraph can be used

 java -jar ap-loader-all.jar converter
Usage: java -cp ap-loader.jar one.converter.<Converter> [options] <input> <output>

Available converters:
  FlameGraph  input.collapsed output.html
  jfr2flame   input.jfr       output.html
  jfr2nflx    input.jfr       output.nflx
  jfr2pprof   input.jfr       output.pprof

however when I run it, I get an error

java -jar ap-loader-all.jar converter FlameGraph input.collapsed collapsed.html
Error: Could not find or load main class FlameGraph
Caused by: java.lang.ClassNotFoundException: FlameGraph