def set_active_editor(oDesign, editorname="3D Modeler"):
    """
    Set the active editor.
    
    Parameters
    ----------
    oDesign : pywin32 COMObject
        The HFSS design upon which to operate.
    editorname : str
        Name of the editor to set as active.  As of this writing "3D Modeler" 
        is the only known valid value.
    
    Returns
    -------
    oEditor : pywin32 COMObject
        The HFSS Editor object.
        
    """
    oEditor = oDesign.SetActiveEditor(editorname)
    
    return oEditor