What is CET as a fee?

Excuse me, could you please clarify what you mean by "CET as a fee"? I'm not immediately familiar with CET being used as a specific term for a fee in the context of cryptocurrency or finance. Could you be referring to a specific platform, exchange, or service that utilizes CET as a fee? Or is CET an acronym for something else entirely? If you could provide some additional context or explanation, I'd be happy to help answer your question to the best of my ability.