'Initialize a geocoder that can parse MediaWiki pages with the GIS
extension enabled.
``format_url`` is a URL string containing \'%s\' where the page name to
request will be interpolated. For example: \'http://www.wiki.com/wiki/%s\'
``transform_string`` is a callable that will make appropriate
replacements to the input string before requesting the page. If None is
given, the default transform_string which replaces \' \' with \'_\' will be
used. It is recommended that you consider this argument keyword-only,
since subclasses will likely place it last.'

def __init__(self, format_url, transform_string=None):

    self.format_url = format_url
    if callable(transform_string):
        self.transform_string = transform_string
