'Returns filter plugins, after loading and caching them if need be'

def _get_filters(self):

    if (self._filters is not None):
        return self._filters.copy()
    plugins = [x for x in self._filter_loader.all()]
    self._filters = dict()
    for fp in plugins:
        self._filters.update(fp.filters())
    self._filters.update(self._get_tests())
    return self._filters.copy()
