toString method Null safety

1. Dart
2. dart:io
3. HttpClientResponseCompressionState
4. toString method

HttpClientResponseCompressionState enum

1. Constants
2. compressed
3. decompressed
4. notCompressed
5. values
6. Properties
7. hashCode
8. index
9. runtimeType
10. Methods
11. noSuchMethod
12. toString
13. Operators
14. operator ==