Understanding `_(...)` in JSON Schema Decoding with Error Handling

    return yield* _(
      json,
      Schema.decodeUnknownEither(AuthorsResponse),
      Either.mapLeft(
        (parseError) =>
          new FormattingError({
            endpoint: endpointUrl,
            message: parseError.message,
          }),
      ),
    );

Effect.gen(function* (_) {})