Add a message to a specific instruction by using (default) the index of the address if specified

        :param msg: the message
        :type msg: string
        :param idx: index of the instruction (the position in the list of the instruction)
        :type idx: int
        :param off: address of the instruction
        :type off: int

def add_inote(self, msg, idx, off=None):
        """
        Add a message to a specific instruction by using (default) the index of the address if specified

        :param msg: the message
        :type msg: string
        :param idx: index of the instruction (the position in the list of the instruction)
        :type idx: int
        :param off: address of the instruction
        :type off: int
        """
        if off is not None:
            idx = self.off_to_pos(off)

        if idx not in self.notes:
            self.notes[idx] = []

        self.notes[idx].append(msg)