How to use the imgkit.source.Source function in imgkit

if self.source.isUrl() or isinstance(self.source.source, list):
            raise self.SourceError('CSS files can be added only to a single file or string')

        if not isinstance(path, list):
            path = [path]

        css_data = []
        for p in path:
            with codecs.open(p, encoding="UTF-8") as f:
                css_data.append(f.read())
        css_data = "\n".join(css_data)

        if self.source.isFile():
            with codecs.open(self.source.to_s(), encoding="UTF-8") as f:
                inp = f.read()
            self.source = Source(
                inp.replace('', self._style_tag(css_data) + ''),
                'string')

        elif self.source.isString():
            if '' in self.source.to_s():
                self.source.source = self.source.to_s().replace(
                    '', self._style_tag(css_data) + '')
            else:
                self.source.source = self._style_tag(css_data) + self.source.to_s()

def __init__(self, url_or_file, source_type, options=None, toc=None, cover=None,
                 css=None, config=None, cover_first=None):
        self.source = Source(url_or_file, source_type)
        self.config = Config() if not config else config
        try:
            self.wkhtmltoimage = self.config.wkhtmltoimage.decode('utf-8')
        except AttributeError:
            self.wkhtmltoimage = self.config.wkhtmltoimage

        self.xvfb = self.config.xvfb

        self.options = {}
        if self.source.isString():
            self.options.update(self._find_options_in_meta(url_or_file))

        if options:
            self.options.update(options)

        self.toc = toc if toc else {}