Return the URI scheme in canonical (lowercase) form, or `default`
        if the original URI reference did not contain a scheme component.

def getscheme(self, default=None):
        """Return the URI scheme in canonical (lowercase) form, or `default`
        if the original URI reference did not contain a scheme component.

        """
        scheme = self.scheme
        if scheme is None:
            return default
        elif isinstance(scheme, bytes):
            return scheme.decode('ascii').lower()
        else:
            return scheme.lower()