Google Cloud Storage Combine files function fails with ApiError: Not Implemented (NodeJs)

When I try to test locally with Firebase Storage Emulator the NodeJs function that needs to combine multiple files in a GCS bucket. I get following error: ApiError: Not Implemented.

Anybody has any idea what this could mean? Is it only associated with the Storage Emulators? Will the function work if I deploy the functions to TEST or PRODUCTION environments?

My code example is the same as in the Google Cloud Storage documentation.

const bucket = admin.storage().bucket("test");

      const file1 = '335eb21f-1eaf-4d01-9a48-8df9c5f6e215_000000000000.csv.gz';
      const file2 = '335eb21f-1eaf-4d01-9a48-8df9c5f6e215_000000000001.csv.gz';
      const destination = 'composed.csv.gz';
      const sources = [file1, file2];

      try {
        await bucket.combine(sources, destination).then((data) => {
          const newFile = data[0];
          const apiResponse = data[1];
          console.log('NEW FILE:', newFile, ' API RESPONSE:', apiResponse);
        });
          }catch(error){
           functions.logger.error('Error', error); 
          }