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General

Your function should parse the passed-in datetime object, add a gigasecond's worth of time to it, and then return the result.
If you're having trouble, remember to take a look at the provided test cases under the Tests tab. These will help you figure out what the expected inputs and outputs of your function(s) should be.
Most of the time, code is read rather than written, and a big number can be a challenge to read. Here are a couple of approaches to making big numbers in your code more readable:
- Using underscores (_) in numeric literals can help offset thousands, hundred-thousands, millions, etc. (ie: 1_000_000 or 10_100_201_330 is far more readable than 1000000 or 10100201330.) See PEP-0515 for more information.
- Scientific notation can be more compact and easier to scan when there are very large numbers (ie: 1e6, 1 is multiplied by 10 raised to the power of 6, which equals 1000000). For more information, see this reference on scientific notation.