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1. This will result in a record with key=null, value="myvalue" and headers={"h0": "v0", "h1": "v1"}
2. This will result in a record with key="mykey", value=null and headers=null
3. This will result in a record with key=null, value=null and headers={"h0": "", "h1": "v1"}
4. This will result in a record with key="mykey", value=null and headers={"h0": null, "h1": "v1"}
5. This will result in a record with key="mykey", value="myvalue" and headers={"NULL": "v0"} This is return an error because headers cannot have a null key.

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