code: func (p *Profiler) Trace(event *topdown.Event) {
  	switch event.Op {
  	case topdown.EvalOp:
  		if expr, ok := event.Node.(*ast.Expr); ok && expr != nil {
  			p.processExpr(expr, event.Op)
  		}
  	case topdown.RedoOp:
  		if expr, ok := event.Node.(*ast.Expr); ok && expr != nil {
  			p.processExpr(expr, event.Op)
  		}
  	}
  }
docs: // Trace updates the profiler state.