code: def visit_enum_existing(
      self,
      key: Union[str, Enum],
      enum_type: Type[Enum],
      consumer: Callable[[Enum], Any],
  ) -> "FluentDict":
      if self._is_not_none(key):
          consumer(self.get_enum(key, enum_type))
  
      return self
  
imports: from enum import Enum
  from typing import Union, Callable, Any, Dict, Optional, Type, List, Generic, TypeVar
label_desc: Use image node_id 18 for calling the FluentDict obj's underlying member method code with example usage: obj.visit_enum_existing(key, enum_type, consumer) and returns: self