def __init__(self, message, main, subtype, attrs):
        """
        @param message: An L{IMessagePart} provider which this structure object
            reports on.

        @param main: A L{str} giving the main MIME type of the message (for
            example, C{"text"}).

        @param subtype: A L{str} giving the MIME subtype of the message (for
            example, C{"plain"}).

        @param attrs: A C{dict} giving the parameters of the I{Content-Type}
            header of the message.
        """
        _MessageStructure.__init__(self, message, attrs)
        self.main = main
        self.subtype = subtype
        self.attrs = attrs

        @param message: An L{IMessagePart} provider which this structure object
            reports on.

        @param main: A L{str} giving the main MIME type of the message (for
            example, C{"text"}).

        @param subtype: A L{str} giving the MIME subtype of the message (for
            example, C{"plain"}).

        @param attrs: A C{dict} giving the parameters of the I{Content-Type}
            header of the message.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/imap4.py