code: def image_groups_download(self, image_group_id):
          
          # Retrieve image group to ensure that it exist
          img_grp = self.image_groups_get(image_group_id)
          if img_grp is None:
              # Return None if image group is unknown
              return None
          else:
              # Reference and information for file image group was created from
              return FileInfo(
                  img_grp.data_file,
                  img_grp.properties[datastore.PROPERTY_MIMETYPE],
                  img_grp.properties[datastore.PROPERTY_FILENAME]
              )
docs: Get data file for image group with given identifier.
  
          Parameters
          ----------
          image_group_id : string
              Unique image group identifier
  
          Returns
          -------
          FileInfo
              Information about image group archive file on disk or None if
              identifier is unknown