MethodCodec constructor Null safety

1. Flutter
2. services
3. MethodCodec
4. MethodCodec constructor

MethodCodec class

1. Constructors
2. MethodCodec
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. decodeEnvelope
8. decodeMethodCall
9. encodeErrorEnvelope
10. encodeMethodCall
11. encodeSuccessEnvelope
12. noSuchMethod
13. toString
14. Operators
15. operator ==