def clear_main_mod_cache(self):
self._main_ns_cache.clear()<EOL>
Clear the cache of main modules.

        Mainly for use by utilities like %reset.

        Examples
        --------

        In [15]: import IPython

        In [16]: _ip.cache_main_mod(IPython.__dict__,IPython.__file__)

        In [17]: len(_ip._main_ns_cache) > 0
        Out[17]: True

        In [18]: _ip.clear_main_mod_cache()

        In [19]: len(_ip._main_ns_cache) == 0
        Out[19]: True