@classmethod
def register_converter(cls, name, converter):
    """
        Register a preset pattern for later use in URL patterns.

        Example usage::

            >>> from datetime import date
            >>> from time import strptime
            >>> class DateConverter(Converter):
            ...     pattern = r'\\d{8}'
            ...     def from_string(self, s):
            ...         return date(*strptime(s, '%d%m%Y')[:3])
            ...
            >>> ExtensiblePattern.register_converter('date', DateConverter)
            >>> ExtensiblePattern('/<:date>')\\
            ...      .match('/01011970')  # doctest:+ELLIPSIS
            PathMatch(..., args=(datetime.date(1970, 1, 1),), kwargs={})
        """
    cls.preset_patterns[name] = converter
