A logrolling or vote-trading is a common practice that elected officials use to pass laws. If you need a support from other elected officials, you promise them to vote for their bill in exchange for their votes. Ukrainian deputies went even further than a simple trading of votes. They trade their ID cards. If you need my vote, you can take my ID card and use it to vote for your bill.
Here is an amazing video that shows a session from Ukraine's Parliament. Click on this link and watch from :29 to 1:00. You will see how a deputy checks in dozens of his colleagues. Then you will see that a head count (424) is far from an actual number of deputies. Finally, you will see how a deputy who uses several ID cards votes for his own proposed bill. Nonetheless, his bill did not pass the parliament.
Here is another video about logrolling Ukrainian deputies.
If you are interested in reading about logrolling, start here.