Need help using MFnWeightGeometryFilter

[desaintdesign]

im new to api, but attempting to write a plugin to transfter cluster membership and weights from one poly object to another. ive written in as a python script but is slow so id like to convert it to python api.
the problem im running into is using MFnWeightGeometryFilter.
should i be able to specify and object in that function: cluster = OpenMayaAnim.MFnWeightGeometryFilter(obj) ?
becuase i get and error: 'Object is incompatible with this method'

for starters, im trying to convert the following code from the maya example plugin, clusterWeightFunction.cpp...

        MSelectionList list;
        MGlobal::getActiveSelectionList(list);

        // Get the cluster
        MFnWeightGeometryFilter cluster;
        MObject dgNode;
        list.getDependNode(0, dgNode);
        if (!cluster.setObject(dgNode))
                return MS::kFailure;

        // Get the object
        MDagPath dagPath;
        MObject component;
        list.getDagPath(1, dagPath, component);

heres what i get:

    import maya.OpenMaya as OpenMaya
    import maya.OpenMayaAnim as OpenMayaAnim

    list = OpenMaya.MSelectionList()
    OpenMaya.MGlobal.getActiveSelectionList(list)

    cluster = OpenMayaAnim.MFnWeightGeometryFilter()
    dgNode = OpenMaya.MObject()

    list.getDependNode(0,dgNode)
    if not (cluster.setObject(dgNode)):

    print 'error'

    dagPath = OpenMaya.MDagPath()
    component = OpenMaya.MObject()
    list.getDagPath(1, dagPath, component)

again, i get this error: 'Object is incompatible with this method'
any ideas what im doing wrong? thanks.