I have already asked IntelliJ to infer nullity on this class. Can you help me make this more accurate.

Note that JSpecify is already used in this repository so it's already imported.

Analyze this Java class and add JSpecify annotations based on:

1. Set the class to be `@NullMarked`

2. Remove all the redundant `@NonNull` annotations that IntelliJ added

3. Check Javadoc @param tags mentioning "null", "nullable", "may be null"

4. Check Javadoc @return tags mentioning "null", "optional", "if available"

5. GraphQL specification semantics (nullable fields, non-null by default)

6. Method implementations that return null or check for null

IntelliJ's infer nullity code analysis isn't comprehensive so feel free to make corrections.

Finally, please check all of this works, by running the NullAway compile check.