code: def extract_code_from_function(function):
      
      if not function.__name__.startswith('fix_'):
          return None
  
      code = re.sub('^fix_', '', function.__name__)
      if not code:
          return None
  
      try:
          int(code[1:])
      except ValueError:
          return None
  
      return code
docs: Return code handled by function.