Makes a given link absolute.

def _make_absolute(self, link):
        """Makes a given link absolute."""

        # Parse the link with stdlib.
        parsed = urlparse(link)._asdict()

        # If link is relative, then join it with base_url.
        if not parsed['netloc']:
            return urljoin(self.base_url, link)

        # Link is absolute; if it lacks a scheme, add one from base_url.
        if not parsed['scheme']:
            parsed['scheme'] = urlparse(self.base_url).scheme

            # Reconstruct the URL to incorporate the new scheme.
            parsed = (v for v in parsed.values())
            return urlunparse(parsed)

        # Link is absolute and complete with scheme; nothing to be done here.
        return link