code: def _flat_set(x):
      if x is None:
          return set()
      if isinstance(x, set):
          return x
      if not isinstance(x, (list, set)):
          x = [x]
      return set(x)
  
imports: import math
  import numbers
  from enum import Enum
  from flash.core.serve.dag.task import flatten, get, get_dependencies, ishashable, istask, reverse_dict, subs, toposort
  from flash.core.serve.dag.utils import key_split
  from flash.core.utilities.imports import _TOPIC_SERVE_AVAILABLE
label_desc: Use image node_id 4 for calling a global function with example usage: _flat_set(x) and returns: set, set, x