apollo-link

const makePromise: <R>(observable: Observable<R>) => Promise<R>;

concat: (
    first: RequestHandler | ApolloLink,
    second: RequestHandler | ApolloLink
) => ApolloLink;

createOperation: (starting: any, operation: GraphQLRequest) => Operation;

empty: () => ApolloLink;

execute: (
    link: ApolloLink,
    operation: GraphQLRequest
) => Observable<
    FetchResult<{ [key: string]: any }, Record<string, any>, Record<string, any>>
>;

from: (links: ApolloLink[]) => ApolloLink;

fromError: <T>(errorValue: any) => Observable<T>;

fromPromise: <T>(promise: Promise<T>) => Observable<T>;

split: (
    test: (op: Operation) => boolean,
    left: ApolloLink | RequestHandler,
    right?: ApolloLink | RequestHandler
) => ApolloLink;

toPromise: <R>(observable: Observable<R>) => Promise<R>;

type FetchResult<
    TData = {
        [key: string]: any;
    },
    C = Record<string, any>,
    E = Record<string, any>
> = ExecutionResult<TData> & {
    extensions?: E;
    context?: C;
};

type NextLink = (operation: Operation) => Observable<FetchResult>;

type RequestHandler = (
    operation: Operation,
    forward: NextLink
) => Observable<FetchResult> | null;