Please check out the documentation for the PDO classes here:
https://canopen.readthedocs.io/en/latest/pdo.html

It shows by example how to set the .trans_type attribute, in your case the value should be 1.

You didn't describe your use case, but I am assuming that you are talking about a TPDO for a remote node (a slave to the SYNC service in that case).

If you actually want to use this library to implement a local node and send a TPDO from the computer when another device has sent a SYNC, then you'll need to wire that up yourself. Subscribe to the SYNC object and call .transmit() on your local PDO representation object when you see the desired point has come. The library does not (yet) implement a full device communication logic through the LocalNode class, but just provides the building blocks for your application code to manage.