'Return the subset of this RcParams dictionary whose keys match,
using :func:`re.search`, the given ``pattern``.
.. note::
Changes to the returned dictionary are *not* propagated to
the parent RcParams dictionary.'

def find_all(self, pattern):

    import re
    pattern_re = re.compile(pattern)
    return RcParams(((key, value) for (key, value) in self.items() if pattern_re.search(key)))
