def init(access_token, environment='production', scrub_fields=None, url_fields=None, **kw):
    """
    Saves configuration variables in this module's SETTINGS.

    access_token: project access token. Get this from the Rollbar UI:
                  - click "Settings" in the top nav
                  - click "Projects" in the left nav
                  - copy-paste the appropriate token.
    environment: environment name. Can be any string; suggestions: 'production', 'development',
                 'staging', 'yourname'
    **kw: provided keyword arguments will override keys in SETTINGS.
    """
    global SETTINGS, agent_log, _initialized, _transforms, _serialize_transform, _threads

    if scrub_fields is not None:
       SETTINGS['scrub_fields'] = list(scrub_fields)
    if url_fields is not None:
       SETTINGS['url_fields'] = list(url_fields)

    # Merge the extra config settings into SETTINGS
    SETTINGS = dict_merge(SETTINGS, kw)
    if _initialized:
        # NOTE: Temp solution to not being able to re-init.
        # New versions of pyrollbar will support re-initialization
        # via the (not-yet-implemented) configure() method.
        if not SETTINGS.get('suppress_reinit_warning'):
            log.warning('Rollbar already initialized. Ignoring re-init.')
        return

    SETTINGS['access_token'] = access_token
    SETTINGS['environment'] = environment

    if SETTINGS.get('allow_logging_basic_config'):
        logging.basicConfig()

    if SETTINGS.get('handler') == 'agent':
        agent_log = _create_agent_log()

    # We will perform these transforms in order:
    # 1. Serialize the payload to be all python built-in objects
    # 2. Scrub the payloads based on the key suffixes in SETTINGS['scrub_fields']
    # 3. Scrub URLs in the payload for keys that end with 'url'
    # 4. Optional - If local variable gathering is enabled, transform the
    #       trace frame values using the ShortReprTransform.
    _serialize_transform = SerializableTransform(safe_repr=SETTINGS['locals']['safe_repr'],
                                                 whitelist_types=SETTINGS['locals']['whitelisted_types'])
    _transforms = [
        ScrubRedactTransform(),
        _serialize_transform,
        ScrubTransform(suffixes=[(field,) for field in SETTINGS['scrub_fields']], redact_char='*'),
        ScrubUrlTransform(suffixes=[(field,) for field in SETTINGS['url_fields']], params_to_scrub=SETTINGS['scrub_fields'])
    ]

    # A list of key prefixes to apply our shortener transform to. The request
    # being included in the body key is old behavior and is being retained for
    # backwards compatibility.
    shortener_keys = [
        ('request', 'POST'),
        ('request', 'json'),
        ('body', 'request', 'POST'),
        ('body', 'request', 'json'),
    ]

    if SETTINGS['locals']['enabled']:
        shortener_keys.append(('body', 'trace', 'frames', '*', 'code'))
        shortener_keys.append(('body', 'trace', 'frames', '*', 'args', '*'))
        shortener_keys.append(('body', 'trace', 'frames', '*', 'kwargs', '*'))
        shortener_keys.append(('body', 'trace', 'frames', '*', 'locals', '*'))

    shortener_keys.extend(SETTINGS['shortener_keys'])

    shortener = ShortenerTransform(safe_repr=SETTINGS['locals']['safe_repr'],
                                   keys=shortener_keys,
                                   **SETTINGS['locals']['sizes'])
    _transforms.append(shortener)
    _threads = queue.Queue()
    events.reset()
    filters.add_builtin_filters(SETTINGS)

    _initialized = True
Saves configuration variables in this module's SETTINGS.

    access_token: project access token. Get this from the Rollbar UI:
                  - click "Settings" in the top nav
                  - click "Projects" in the left nav
                  - copy-paste the appropriate token.
    environment: environment name. Can be any string; suggestions: 'production', 'development',
                 'staging', 'yourname'
    **kw: provided keyword arguments will override keys in SETTINGS.