'Unregister a provider
:param str entry_point: provider to unregister (entry point syntax).'

def unregister(self, entry_point):

    if (entry_point not in self.registered_extensions):
        raise ValueError('Extension    not    registered')
    ep = EntryPoint.parse(entry_point)
    self.registered_extensions.remove(entry_point)
    if (self._extensions_by_name is not None):
        del self._extensions_by_name[ep.name]
    for (i, ext) in enumerate(self.extensions):
        if (ext.name == ep.name):
            del self.extensions[i]
            break
