def ExportPowderList(G2frame):
    """Returns a list of extensions supported by :func:`GSASIIIO:ExportPowder`
    This is used in :meth:`GSASIIimgGUI.AutoIntFrame` only. 
    
    :param wx.Frame G2frame: the GSAS-II main data tree window
    """
    extList = []
    for obj in G2frame.exporterlist:
        if 'powder' in obj.exporttype:
            try:
                obj.Writer
                extList.append(obj.extension)
            except AttributeError:
                pass
    return extList
