This method creates a dictionary to map plant IDs to
        GPIO pins are associated in triples.
        Each ID gets a light, a fan, and a mist nozzle.

def form_GPIO_map(self):
        """ This method creates a dictionary to map plant IDs to
        GPIO pins are associated in triples.
        Each ID gets a light, a fan, and a mist nozzle.
        """
        # Compute bank/pins/IOexpander address based on ID
        if self.ID == 1:
            self.IOexpander = 0x20
            self.bank = 0
            self.fan = 2
            self.light = 3
            self.valve = 4
        elif self.ID == 2:
            self.IOexpander = 0x20
            self.bank = 0
            self.fan = 5
            self.light = 6
            self.valve = 7
        elif self.ID == 3:
            self.IOexpander = 0x20
            self.bank = 1
            self.fan = 0
            self.light = 1
            self.valve = 2
        elif self.ID == 4:
            self.IOexpander = 0x20
            self.bank = 1
            self.fan = 3
            self.light = 5
            self.valve = 6
        else:
            raise InvalidIOMap(
                "Mapping not available for ID: " + str(self.ID))

        # Check to make sure reserved pins are not requested
        if (self.bank == 0) and (min(self.fan, self.light, self.valve) < 2):
            raise InvalidIOMap(
                "Pins A0 and A1 are reserved for other functions")

        self.GPIO_dict = [{'ID': self.ID, 'bank': self.bank,
                           'fan': self.fan, 'valve': self.valve, 'light': self.light}]

        # Append dictionary to class and resort dictionary by ID # if needed
        ControlCluster.GPIOdict.append(self.GPIO_dict)