how to rename the columns "firstName", "lastName", "email" in the code?

Hi, can you tell me how to rename the columns “firstName”, “lastName”, “email” in the code? Renamed everything I wanted, except these 3. Thanks in advance for the answer.
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Can you post a small snippet of your code for reference of how you’re building the grid and how you renamed the other columns?

It seems you are working with the CRM tutorial application. In that case, the setColumn() calls have a setHeader(...) method at the end that you need to change.