Model with units defined in a component don't get properly converted

[agarny]

This model describes the following model:

def model van_der_pol_model_1928 as
    def comp main as
        def unit per_second as
            unit second {expo: -1};
        enddef;

        var time: second;
        var x: dimensionless {init: -2};
        var y: dimensionless {init: 0};
        var epsilon: dimensionless {init: 1};

        ode(x, time) = y*1{per_second};
        ode(y, time) = (epsilon*(1{dimensionless}-sqr(x))*y-x)*1{per_second};
    enddef;
enddef;

As we can see, per_second is defined within the main component. If you convert this model to CellML 2.0 using cellml1to2.xsl, you end up with this model, which also defines per_second in the main component. However, CellML 2.0 only allows units to be defined in the model element (see section 8 of https://www.cellml.org/specifications/cellml_2.0). So, here, we end up with an invalid CellML 2.0 file.