code: def fuzzy_not(v):
      """
      Not in fuzzy logic
  
      Return None if `v` is None else `not v`.
  
      Examples
      ========
  
      >>> from sympy.core.logic import fuzzy_not
      >>> fuzzy_not(True)
      False
      >>> fuzzy_not(None)
      >>> fuzzy_not(False)
      True
  
      """
      if v is None:
          return v
      else:
          return not v
  
imports: from __future__ import annotations
  from typing import Optional
label_desc: Use image node_id 5 for calling a global function with example usage: fuzzy_not(v) and returns: v, unknown