docs: def image_files_download(self, image_id):
          """Get data file for image with given identifier.
  
          Parameters
          ----------
          image_id : string
              Unique image identifier
  
          Returns
          -------
          FileInfo
              Information about image file on disk or None if identifier
              is unknown
          """
          # Retrieve image to ensure that it exist
          img = self.image_files_get(image_id)
          if img is None:
              # Return None if image is unknown
              return None
          else:
              # Reference and information for original uploaded file
              return FileInfo(
                  img.image_file,
                  img.properties[datastore.PROPERTY_MIMETYPE],
                  img.properties[datastore.PROPERTY_FILENAME]
              )