def loadAllMayaPlugins():
    import logging
    logger = logging.getLogger('pymel')
    logger.debug("loading all maya plugins...")
    for plugin in mayaPlugins():
        try:
            maya.cmds.loadPlugin( plugin, quiet=1 )
        except RuntimeError: pass
    logger.debug("...done loading all maya plugins")
will load all maya-installed plugins
dataset/ETHPy150Open CountZer0/PipelineConstructionSet/python/maya/site-packages/pymel-1.0.5/pymel/api/plugins.py/loadAllMayaPlugins