def METHOD_NAME(username, api_key, **kwargs):
    """
    Set set session credentials and config (not saved to file).
    If unspecified, credentials and config are searched for in `.plotly` dir.
    :param (str) username: The username you'd use to sign in to Plotly
    :param (str) api_key: The api key associated with above username
    :param (list|optional) stream_ids: Stream tokens for above credentials
    :param (str|optional) proxy_username: The un associated with with your Proxy
    :param (str|optional) proxy_password: The pw associated with your Proxy un
    :param (str|optional) plotly_domain:
    :param (str|optional) plotly_streaming_domain:
    :param (str|optional) plotly_api_domain:
    :param (bool|optional) plotly_ssl_verification:
    :param (bool|optional) plotly_proxy_authorization:
    :param (bool|optional) world_readable:
    """
    # TODO: verify these _credentials with plotly
    # kwargs will contain all our info
    kwargs.update(username=username, api_key=api_key)
    # raise error if key isn't valid anywhere
    for key in kwargs:
        if key not in CREDENTIALS_KEYS and key not in CONFIG_KEYS:
            raise _plotly_utils.exceptions.PlotlyError(
                "{} is not a valid config or credentials key".format(key)
            )
    # add credentials, raise error if type is wrong.
    for key in CREDENTIALS_KEYS:
        if key in kwargs:
            if not isinstance(kwargs[key], CREDENTIALS_KEYS[key]):
                raise _plotly_utils.exceptions.PlotlyError(
                    "{} must be of type '{}'".format(key, CREDENTIALS_KEYS[key])
                )
            _session["credentials"][key] = kwargs[key]
    # add config, raise error if type is wrong.
    for key in CONFIG_KEYS:
        if key in kwargs:
            if not isinstance(kwargs[key], CONFIG_KEYS[key]):
                raise _plotly_utils.exceptions.PlotlyError(
                    "{} must be of type '{}'".format(key, CONFIG_KEYS[key])
                )
            _session["config"][key] = kwargs.get(key)
    # add plot options, raise error if type is wrong.
    for key in PLOT_OPTIONS:
        if key in kwargs:
            if not isinstance(kwargs[key], CONFIG_KEYS[key]):
                raise _plotly_utils.exceptions.PlotlyError(
                    "{} must be of type '{}'".format(key, CONFIG_KEYS[key])
                )
            _session["plot_options"][key] = kwargs.get(key)