code: func (c *Files) GetThumbnail(in *GetThumbnailInput) (out *GetThumbnailOutput, err error) {
  	body, l, err := c.download("/files/get_thumbnail", in, nil)
  	if err != nil {
  		return
  	}
  
  	out = &GetThumbnailOutput{body, l}
  	return
  }
docs: // GetThumbnail a thumbnail for a file. Currently thumbnails are only generated for the
  // files with the following extensions: png, jpeg, png, tiff, tif, gif and bmp.