Couldn't generate code for the following reason:
Invalid units uApmmsq on variable.; 
  In MathML apply element with ID Vm_diff_calculation.
  In MathML math element.
  In CellMLComponent element with cmeta:id membrane with name membrane.
  In Model element with cmeta:id hunter_mcnaughton_noble_1975_version02 with name hunter_mcnaughton_noble_1975_version02.