/**
 * Callback hooks invoked during the transport lifecycle.
 */
export type TransportCallbacks = {
    /** Invoked when a transport connection is initialized. */
    onInitialize: (message: any) => void;
    /** Invoked when a transport connection is finalized. */
    onFinalize: (message: any) => void;
    /** Invoked when the transport receives a message. */
    onMessage: (message: any) => void;
};
/** Helper class for Python / Jupyter integration */
export declare class Transport {
    /**
     * Registers lifecycle callbacks shared by all transport instances.
     * @param callbacks Partial callback set to install.
     */
    static setCallbacks({ onInitialize, onFinalize, onMessage }: Partial<TransportCallbacks>): void;
    /** Human-readable transport name. */
    name: string;
    /** Queue of inbound messages received before callbacks are ready. */
    _messageQueue: never[];
    /** Arbitrary user data associated with the transport instance. */
    userData: {};
    /** Whether the transport has been finalized. */
    _destroyed: boolean;
    /**
     * Creates a transport instance.
     * @param name Human-readable transport name.
     */
    constructor(name?: string);
    /**
     * Return a root DOM element for this transport connection
     * @returns default implementation returns document.body
     * Jupyter Notebook transports will return an element associated with the notebook cell
     */
    getRootDOMElement(): HTMLElement | null;
    /**
     * Sends a JSON message through the transport back-channel.
     */
    sendJSONMessage(): void;
    /**
     * Sends a binary message through the transport back-channel.
     */
    sendBinaryMessage(): void;
    /**
     * Marks the transport as initialized and emits the initialize callback.
     * @param options Additional payload fields merged into the callback message.
     */
    _initialize(options?: {}): void;
    /**
     * Marks the transport as finalized and emits the finalize callback.
     * @param options Additional payload fields merged into the callback message.
     */
    _finalize(options?: {}): void;
    /**
     * Delivers a received message to the registered message callback.
     * @param message Additional payload fields merged into the callback message.
     */
    _messageReceived(message?: {}): void;
    /**
     * Serializes an object to JSON while tolerating circular references where possible.
     * @param v Value to serialize.
     * @returns A JSON string with cycles removed or deduplicated where possible.
     */
    static _stringifyJSONSafe(v: any): string;
}
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