def __init__(self, usb, chunk_kb=1024):
        """Constructs a FastbootProtocol instance.

        Args:
          usb: UsbHandle instance.
          chunk_kb: Packet size. For older devices, 4 may be required.
        """
        self.usb = usb
        self.chunk_kb = chunk_kb
Constructs a FastbootProtocol instance.

        Args:
          usb: UsbHandle instance.
          chunk_kb: Packet size. For older devices, 4 may be required.
        
adb/fastboot.py