The MeshSet class represents a container that allows to collect a set of Meshes, where every Mesh corresponds to a layer of MeshLab. From this class, you can apply all the filters of meshlab by calling the :pymeshlab.MeshSet.apply_filter method.
In every non-empty MeshSet, there is a selected mesh, that can be accessed using the method :pymeshlab.MeshSet.current_mesh.
meshlab.MeshSet