uploaderIsAxios () {
    if (
      this.hasUploader() &&
      typeof this.context.uploader.request === 'function' &&
      typeof this.context.uploader.get === 'function' &&
      typeof this.context.uploader.delete === 'function' &&
      typeof this.context.uploader.post === 'function'
    ) {
      return true
    }
    return false
  }
Check if the given uploader is axios instance. This isn't a great way of
testing if it is or not, but AFIK there isn't a better way right now:

https://github.com/axios/axios/issues/737