class_docstr: Helper base class for the :class:`Domain` and :class:`Sample` classes.
  
  It implements common logic for creation, representation, type conversion
  and serialisation.
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docstr: Return the flattened version of the recursive dict, i.e. without
  nested dicts.
  
  The keys of the nested subdomains are collected in a tuple to create a
  new unique key. For the sake of type consistency, the key of a
  non-nested subdomain is converted to a tuple with a single element.
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code: def flatten(self):
      """Return the flattened version of the recursive dict, i.e. without
      nested dicts.
  
      The keys of the nested subdomains are collected in a tuple to create a
      new unique key. For the sake of type consistency, the key of a
      non-nested subdomain is converted to a tuple with a single element.
      """
      return {keys: val for keys, val in _deepiter_dict(self._data)}
  
imports: import ast
  import copy
  import os
  import pickle
  import random
  from collections import namedtuple
  from typing import Tuple
label_desc: Use image node_id 9 for calling the _RecursiveDict obj's underlying member method code with example usage: obj.flatten() and returns: unknown