As stated in the documentation, it states that the classes supports the foramtes list in open asset import library, that includes the following:-

https://assimp.sourceforge.net/main_features_formats.html

• Autodesk ( .fbx )
• Collada ( .dae )
• glTF ( .gltf, .glb )
• Blender 3D ( .blend )
• 3ds Max 3DS ( .3ds )
• 3ds Max ASE ( .ase )
• Wavefront Object ( .obj )
• Industry Foundation Classes (IFC/Step) ( .ifc )
• XGL ( .xgl,.zgl )
• Stanford Polygon Library ( .ply )
• {}AutoCAD DXF{*} ( .dxf )
• LightWave ( .lwo )
• LightWave Scene ( .lws )
• Modo ( .lxo )
• Stereolithography ( .stl )
• DirectX X ( .x )
• AC3D ( .ac )
• Milkshape 3D ( .ms3d )
• * TrueSpace ( .cob,.scn )

Yet, I tried loading a .blend and a .glb files, and they basically didn't load, it only worked for me with .obj and .stl files.