Apollo Server and TypeScript: Type 'GraphQLApi' has no properties in common with type 'DataSource<object>'

I'm setting up an interface between our NextJS Front and a series of backends. The interface will convert the various backs' REST or GraphQL APIs into a unitary GraphQL API. I'm using the library apollo-datasource-graphql to translate a back that offers a GraphQL API into a datasource to use with Apollo Server. I'm running into a fair number of TypeScript issues. At present TS complains about my definition of the Apollo data sources

index.ts:10:25 - error TS2559: Type 'InterfaceGraphQLApi' has no properties in common with type 'DataSource<object>'.

10   dataSources: () => ({ gqlApi: new InterfaceGraphQLApi() })
                           ~~~~~~

  node_modules/apollo-server-core/dist/graphqlOptions.d.ts:31:5
    31     [name: string]: DataSource<TContext>;
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    The expected type comes from this index signature.

here

const server = new ApolloServer({
  typeDefs,
  resolvers,
  dataSources: () => ({ gqlApi: new InterfaceGraphQLApi() })
});

where InterfaceGraphQLApi starts thusly

import { GraphQLDataSource } from "apollo-datasource-graphql";
export default class InterfaceGraphQLApi extends GraphQLDataSource {
  baseURL = "http://localhost:4545/admin/api";

In the source files for Apollo-datasource-graphql (node_modules/src/GraphQLDataSource.ts) I see

export class GraphQLDataSource<TContext = any> {

So it seems that I could pass some kind of type parameter, which would be the same as Datasource<object> I might be OK? But I'm far out of my TypeScript/Apollo knowledge zone, so I'm wandering lost here. Any guidance much appreciated!