Is there a way to find out what meshes are supposed to be combined in Assimp?

I'm working on my model loader which uses assimp to convert to a common proprietary file format. I know that Assimp separates multi-material meshes into different meshes per material. To work around this, before I used to simply combine consider all the meshes as submeshes in the model file upon import. Now, I want to figure out which submeshes are from multi-material meshes so I can combine only those - is there a way to do this within Assimp?