code: def does_keychain_exist(dict_, list_):
      
      for key in list_:
          if key not in dict_:
              return False
          dict_ = dict_[key]
      return True
docs: Check if a sequence of keys exist in a nested dictionary.
  
      Parameters
      ----------
      dict_ : Dict[str/int/tuple, Any]
      list_ : List[str/int/tuple]
  
      Returns
      -------
      keychain_exists : bool
  
      Examples
      --------
      >>> d = {'a': {'b': {'c': 'd'}}}
      >>> l_exists = ['a', 'b']
      >>> does_keychain_exist(d, l_exists)
      True
  
      >>> l_no_existant = ['a', 'c']
      >>> does_keychain_exist(d, l_no_existant)
      False