请问应该怎么将refprop中的介质导入modelica基础库里的组件呢，我已经下了ExternalRefProp，我这样写的代码一直显示语法有问题：
model Model3
import ExternalRefProp
import ExternalRefProp.Medias
import ExternalRefProp.Interfaces

Modelica.Fluid.Sources.MassFlowSource_h boundary(nPorts=1,redeclare package Medium = ExternalRefProp.Medias.R410A)
annotation (Placement(transformation(origin = {-125.533, -17.7333}, extent = {{-10, -10}, {10, 10}})));

end Model3;