class Agg extends Bundle {
      val foo = Bool()
      val bar = Bool()
    }
    class FixedIO extends Bundle {
      val elem = Probe(Bool())
      val agg = Probe(new Agg())
    }

    class ExampleRaw extends FixedIORawModule[FixedIO](new FixedIO()) {

      val elemWire = Wire(Bool())
      elemWire := false.B
      probe.define(io.elem, probe.ProbeValue(elemWire))

      val aggWire = Wire(new Agg())
      aggWire := DontCare
      probe.define(io.agg, probe.ProbeValue(aggWire))
    }

    class ExampleExt extends FixedIOExtModule[FixedIO](new FixedIO())

    class Parent extends Module {
      val childRaw = Module(new ExampleRaw())
      val childExt = Module(new ExampleExt())
      val outElemRaw = IO(Bool())
      val probeElemWireRaw = Wire(Probe(Bool()))
      outElemRaw := probe.read(probeElemWireRaw)
      probeElemWireRaw :<>= childRaw.io.elem
      val probeElemWireExt = Wire(Probe(Bool()))
      val outElemExt = IO(Bool())
      outElemExt := probe.read(probeElemWireExt)
      probeElemWireExt :<>= childExt.io.elem

      
      val outAggRaw = IO(new Agg())
      val probeAggWireRaw = Wire(Probe(new Agg()))
      outAggRaw := probe.read(probeAggWireRaw)
      probeAggWireRaw :<>= childRaw.io.agg
      val probeAggWireExt = Wire(Probe(new Agg()))
      val outAggExt = IO(new Agg())
      outAggExt := probe.read(probeAggWireExt)
      probeAggWireExt :<>= childExt.io.agg
    }