def version(self) -> str:
        """
        Return the HTTP version used by the server, e.g. '1.1'.

        Assume HTTP/1.1 if version is not available.

        """
        mapping = {
            9: '0.9',
            10: '1.0',
            11: '1.1',
            20: '2.0',
        }
        fallback = 11
        version = None
        try:
            raw = self._orig.raw
            if getattr(raw, '_original_response', None):
                version = raw._original_response.version
            else:
                version = raw.version
        except AttributeError:
            pass
        return mapping[version or fallback]

        Return the HTTP version used by the server, e.g. '1.1'.

        Assume HTTP/1.1 if version is not available.

        
httpie/models.py