import { BaseLoaderOptions, Loader, Source } from '@graphql-tools/utils';
/**
 * Additional options for loading from Apollo Engine
 */
export interface ApolloEngineOptions extends BaseLoaderOptions {
    engine: {
        endpoint?: string;
        apiKey: string;
    };
    graph: string;
    variant: string;
    headers?: Record<string, string>;
}
/**
 * This loader loads a schema from Apollo Engine
 */
export declare class ApolloEngineLoader implements Loader<ApolloEngineOptions> {
    private getFetchArgs;
    canLoad(ptr: string): Promise<boolean>;
    canLoadSync(ptr: string): boolean;
    load(pointer: string, options: ApolloEngineOptions): Promise<Source[]>;
    loadSync(pointer: string, options: ApolloEngineOptions): Source[];
}
/**
 * @internal
 */
export declare const SCHEMA_QUERY = "\n  query GetSchemaByTag($tag: String!, $id: ID!) {\n    service(id: $id) {\n      ... on Service {\n        __typename\n        schema(tag: $tag) {\n          document\n        }\n      }\n    }\n  }\n";
