message: Replaced ExpressionModelType "None" with "none" in Python
  This is to avoid the conflict with Python's built-in keyword "None".
diff: @@ -170,7 +170,7 @@ PYBIND11_MODULE(eos, eos_module)
  py::enum_<morphablemodel::MorphableModel::ExpressionModelType>(
  morphable_model, "ExpressionModelType",
  "The type of the expression model that a MorphableModel contains.")
  - .value("None", morphablemodel::MorphableModel::ExpressionModelType::None)
  + .value("none", morphablemodel::MorphableModel::ExpressionModelType::None)
  .value("Blendshapes", morphablemodel::MorphableModel::ExpressionModelType::Blendshapes)
  .value("PcaModel", morphablemodel::MorphableModel::ExpressionModelType::PcaModel);
  