code: def visit_str_existing(
      self, key: Union[str, Enum], consumer: Callable[[str], Any]
  ) -> "FluentDict":
      if self._is_not_none(key):
          consumer(self.get(key))
      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 6 for calling the FluentDict obj's underlying member method code with example usage: obj.visit_str_existing(key, consumer) and returns: self