class_docstr: A file-like object that is backed by a BytesIO() object whose contents
  is loaded from a BlobProperty in the app engine datastore.
code: def __init__(self, *args, **kwargs):
      super(DatastoreFile, self).__init__(*args, **kwargs)
      self.data = BytesIO()
  
imports: import time
  from google.appengine.api import memcache
  from google.appengine.ext import db
  from whoosh.compat import BytesIO
  from whoosh.index import TOC, FileIndex, _DEF_INDEX_NAME
  from whoosh.filedb.filestore import ReadOnlyError, Storage
  from whoosh.filedb.structfile import StructFile
label_desc: Use image node_id 1 to create a new DatastoreFile object from inherited base classes: db with example: obj = DatastoreFile()