code: def istainted(arg, taint=None):
      
  
      if not issymbolic(arg):
          return False
      if taint is None:
          return len(arg.taint) != 0
      for arg_taint in arg.taint:
          m = re.match(taint, arg_taint, re.DOTALL | re.IGNORECASE)
          if m:
              return True
      return False
docs: Helper to determine whether an object if tainted.
      :param arg: a value or Expression
      :param taint: a regular expression matching a taint value (eg. 'IMPORTANT.*'). If None, this function checks for any taint value.