A provider that lets you mock loading state

LoadingProvider.jsx

const LoadingProvider = (props) => {
  const link = new ApolloLink((operation) => {
    return new Observable(() => {});
  });
  
  const client = new ApolloClient({
    link,
    cache: new InMemoryCache(),
  });
  
  return (
    <ApolloProvider client={client}>
      {props.children}
    </ApolloProvider>
  );
};

Where does Observable come from? Do you have to bring in RxJS just to get this to work?