Question: Trace: What is an unknow procedure and is it tracable at all?

I have tried to understand why ODESteps cannot find a solution for cases where an ODE can separated into a polynomial expression and an ODE.

or example, when I trace like this

restart;
trace(Student:-ODEs:-ODESteps:-ModuleApply);
printlevel:=10;
Student:-ODEs:-ODESteps:-ModuleApply(x*(diff(y(x), x)) = 0);
printlevel:=1

trace is tracing an unknown procedure

and not showing any further details of this procedure.
What unknow function/procedure is traced?

Can, in this particular case, the message "Cannot compute integral"   be traced (it’s not an error message, which are traceable).

I have tried to increase printlevel which reveals some unkown procedures but did not get down to this one. Hence my questions.

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