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