no, almost!!!
this is my code:
MObject oThis = thisMObject();
MDataHandle origMeshSrcHandle = data.inputValue(inMeshAttr);
MObject inMesh = origMeshSrcHandle.asMesh();
//inMesh:
MFnMesh inMesh_fn(inMesh, &stat);
MFnMeshData meshDataFn;
MObject outMeshObj = meshDataFn.create();
MFnMesh outMeshFn;
outMeshFn.copy(inMesh, outMeshObj);
outMeshFn.deleteFace(12);
MPlug oMPlug(oThis, outMeshAttr);
oMPlug.selectAncestorLogicalIndex(0, outsAttr);
oMPlug.setMObject(outMeshObj);