def initialize(self):
        '''List all datasets for a given ...'''
        fmt = guess_format(self.source.url)
        # if format can't be guessed from the url
        # we fallback on the declared Content-Type
        if not fmt:
            response = requests.head(self.source.url)
            mime_type = response.headers.get('Content-Type', '').split(';', 1)[0]
            if not mime_type:
                msg = 'Unable to detect format from extension or mime type'
                raise ValueError(msg)
            fmt = guess_format(mime_type)
            if not fmt:
                msg = 'Unsupported mime type "{0}"'.format(mime_type)
                raise ValueError(msg)
        graph = self.parse_graph(self.source.url, fmt)
        self.job.data = {'graph': graph.serialize(format='json-ld', indent=None)}
List all datasets for a given ...