PropertyDataType d2Value(VariableArray const &variable_array, Variable const variable1, Variable const variable2, ParameterLib::SpatialPosition const &pos, double const t, double const dt) const override
Default implementation: 2nd derivative of any constant property is zero.
std::variant< double, Eigen::Matrix< double, 2, 1 >, Eigen::Matrix< double, 3, 1 >, Eigen::Matrix< double, 2, 2 >, Eigen::Matrix< double, 3, 3 >, Eigen::Matrix< double, 4, 1 >, Eigen::Matrix< double, 6, 1 >, Eigen::MatrixXd > PropertyDataType