<?xml version="1.0" encoding="UTF-8"?>
<!-- CellML Test Suite. https://github.com/MichaelClerx/cellml-validation -->
<!-- CellML 1.0, 4.2.3: The MathML "CellML subset"
Logical constants: true and false -->
<model name="mathml_logic_constants"
xmlns="http://www.cellml.org/cellml/1.0#"
xmlns:cellml="http://www.cellml.org/cellml/1.0#">
<component name="A">
<variable name="x" units="dimensionless" initial_value="0" />
<variable name="iftrue" units="dimensionless" />
<variable name="iffalse" units="dimensionless" />
<math xmlns="http://www.w3.org/1998/Math/MathML">
<apply>
<eq/>
<ci>iftrue</ci>
<piecewise>
<piece>
<cn cellml:units="dimensionless">1</cn>
<apply>
<eq />
<apply>
<eq />
<ci>x</ci>
<cn cellml:units="dimensionless">0</cn>
</apply>
<true />
</apply>
</piece>
<otherwise>
<cn cellml:units="dimensionless">0</cn>
</otherwise>
</piecewise>
</apply>
<apply>
<eq/>
<ci>iffalse</ci>
<piecewise>
<piece>
<cn cellml:units="dimensionless">1</cn>
<apply>
<eq />
<apply>
<eq />
<ci>x</ci>
<cn cellml:units="dimensionless">0</cn>
</apply>
<false />
</apply>
</piece>
<otherwise>
<cn cellml:units="dimensionless">0</cn>
</otherwise>
</piecewise>
</apply>
</math>
</component>
</model>
'BooleanTrue' object has no attribute 'as_coeff_Add'
results in