upload(fileIDs: string[]) {
    // emit the event for progress tracking to uppy
    this.uppy.emit("upload-start", this.uppy.getFiles())

    const promises = fileIDs.map((fileId) => {
      const file = this.uppy.getFile(fileId)

      return new Promise((resolve, rejects) => {
      // some upload hook
        this.uploadHook(file.data)
          .then((result: any) => {
            // event emitting is important for uppy to keep track of the actual progress state
            this.uppy.emit("upload-success", file, result)
            resolve(result)
          })
          .catch((err: any) => {
            // event emitting is important for uppy to keep track of the actual progress state
            this.uppy.emit("upload-error", file, err)
            rejects(err)
          })
      })
    })

    return Promise.all(promises).then(() => {}) // returned promise needs to be Promise<void>
  }