File "/home/user/.local/lib/python3.7/site-packages/trezorlib/client.py", line 117, in cancel
    self._raw_write(messages.Cancel())
  File "/home/user/.local/lib/python3.7/site-packages/trezorlib/client.py", line 126, in _raw_write
    self.transport.write(msg)
  File "/home/user/.local/lib/python3.7/site-packages/trezorlib/transport/protocol.py", line 117, in write
    self.protocol.write(message)
  File "/home/user/.local/lib/python3.7/site-packages/trezorlib/transport/protocol.py", line 151, in write
    self.handle.write_chunk(chunk)
  File "/home/user/.local/lib/python3.7/site-packages/trezorlib/transport/webusb.py", line 65, in write_chunk
    assert self.handle is not None