docs: def transform_op(self, op, value):
      """For comparisons, if the value is None (null), the '=' operator must be replaced with ' is '
      and the '!=' operator must be replaced with ' is not '. This function handles that conversion.
      It's up to the caller to call this function only on comparisons and not on assignments.
      """
      if value is None:
        if _EQ_RE.match(op):
          return "is"
        elif _NEQ_RE.match(op):
          return "is not"
  
      return op