def __init__(self, sdat, istep, msg):
self.sdat = sdat<EOL>self.istep = istep<EOL>self.msg = msg<EOL>super().__init__(sdat, istep, msg)<EOL>
Initialization of instances:

        Args:
            sdat (:class:`~stagpy.stagyydata.StagyyData`): the StagyyData
                instance for which the request was made.
            istep (int): the invalid time step index.
            msg (str): the error message.

        Attributes:
            sdat (:class:`~stagpy.stagyydata.StagyyData`): the StagyyData
                instance for which the request was made.
            istep (int): the invalid time step index.
            msg (str): the error message.