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.

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