def url(self, schemes=None):
        """
        :param schemes: a list of strings to use as schemes, one will chosen randomly.
        If None, it will generate http and https urls.
        Passing an empty list will result in schemeless url generation like "://domain.com".

        :returns: a random url string.
        """
        if schemes is None:
            schemes = ['http', 'https']

        pattern = '{}://{}'.format(
            self.random_element(schemes) if schemes else "",
            self.random_element(self.url_formats),
        )

        return self.generator.parse(pattern)
:param schemes: a list of strings to use as schemes, one will chosen randomly.
        If None, it will generate http and https urls.
        Passing an empty list will result in schemeless url generation like "://domain.com".

        :returns: a random url string.