code: def pullup(self, pin, enabled):
          
          self._validate_pin(pin)
          if enabled:
              self.gppu[int(pin/8)] |= 1 << (int(pin%8))
          else:
              self.gppu[int(pin/8)] &= ~(1 << (int(pin%8)))
          self.write_gppu()
docs: Turn on the pull-up resistor for the specified pin if enabled is True,
          otherwise turn off the pull-up resistor.