Returns list of names of pressed buttons.

def buttons_pressed(self):
        """
        Returns list of names of pressed buttons.
        """
        for b in self._buffer_cache:
            fcntl.ioctl(self._button_file(b), self.EVIOCGKEY, self._buffer_cache[b])

        pressed = []
        for k, v in self._buttons.items():
            buf = self._buffer_cache[v['name']]
            bit = v['value']

            if bool(buf[int(bit / 8)] & 1 << bit % 8):
                pressed.append(k)

        return pressed