How to use the graphistry.util.warn function in graphistry

response.raise_for_status()
            jres = response.json()

            cver = sys.modules['graphistry'].__version__
            if  'pygraphistry' in jres and 'minVersion' in jres['pygraphistry'] and 'latestVersion' in jres['pygraphistry']:
                mver = jres['pygraphistry']['minVersion']
                lver = jres['pygraphistry']['latestVersion']
                if util.compare_versions(mver, cver) > 0:
                    util.warn('Your version of PyGraphistry is no longer supported (installed=%s latest=%s). Please upgrade!' % (cver, lver))
                elif util.compare_versions(lver, cver) > 0:
                    print('A new version of PyGraphistry is available (installed=%s latest=%s).' % (cver, lver))

            if jres['success'] is not True:
                util.warn(jres['error'])
        except Exception as e:
            util.warn('Could not contact %s. Are you connected to the Internet?' % PyGraphistry._config['hostname'])

def _get_initial_config():
    config = default_config.copy()
    for path in config_paths:
        try:
            with open(path) as config_file:
                config.update(json.load(config_file))
        except ValueError as e:
            util.warn('Syntax error in %s, skipping. (%s)' % (path, e.message))
            pass
        except IOError:
            pass

    env_config = {k: os.environ.get(v) for k, v in EnvVarNames.items()}
    env_override = {k: v for k, v in env_config.items() if v != None}
    config.update(env_override)
    if not config['certificate_validation']:
        requests.packages.urllib3.disable_warnings()
    return config

def server(value=None):
        """Get the hostname of the server or set the server using hostname or aliases.
        Supported aliases: 'localhost', 'staging', 'labs'.
        Also set via environment variable GRAPHISTRY_HOSTNAME."""
        if value is None:
            return PyGraphistry._config['hostname']

        # setter
        shortcuts = {'dev': 'localhost:3000',
                     'staging': 'staging.graphistry.com',
                     'labs': 'labs.graphistry.com'}
        if value in shortcuts:
            resolved = shortcuts[value]
            PyGraphistry._config['hostname'] = resolved
            util.warn('Resolving alias %s to %s' % (value, resolved))
        else:
            PyGraphistry._config['hostname'] = value