code: def refresh(self, document):
  		
  		try:
  			old_cache_size = self.cache_size
  			self.cache_size = 0
  			obj = self.query(type(document)).filter_by(mongo_id=document.mongo_id).one()
  		finally:
  			self.cache_size = old_cache_size
  		self.cache_write(obj)
  		return obj
docs: Load a new copy of a document from the database.  does not
  			replace the old one