Return the filter rule

        :param: _filter a zobjects.FilterRule or the filter name
        :param: way string discribing if filter is for 'in' or 'out' messages
        :returns: a zobjects.FilterRule

def get_filter_rule(self, _filter, way='in'):
        """ Return the filter rule

        :param: _filter a zobjects.FilterRule or the filter name
        :param: way string discribing if filter is for 'in' or 'out' messages
        :returns: a zobjects.FilterRule"""
        if isinstance(_filter, zobjects.FilterRule):
            _filter = _filter.name
        for f in self.get_filter_rules(way=way):
            if f.name == _filter:
                return f
        return None