<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def is_connected(self):
 """ Checks if the USB device is still connected """

        if self._is_open:
            err = hidapi.hid_read_timeout(self._device, ffi.NULL, 0, 0)
            if err == -1:
                return False
            else:
                return True
        else:
            en = Enumeration(vid=self.vendor_id, pid=self.product_id).find(path=self.path)
            if len(en) == 0:
                return False
            else:
                return True