class_docstr: Base class for any frontend that gets exposed by LightningFlows.
  
  The flow attribute will be set by the app while bootstrapping.
code: def __init__(self) -> None:
      self.flow: Optional["LightningFlow"] = None
  
imports: from abc import ABC, abstractmethod
  from typing import TYPE_CHECKING, Optional
label_desc: Use image node_id 1 to create a new Frontend object from inherited base classes: ABC with example: obj = Frontend()