CommandString constructor Null safety

1. sendbird_sdk
2. command_type
3. CommandString
4. CommandString constructor

CommandString class

1. Constructors
2. CommandString
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Static methods
12. isAdminMessage
13. isFileMessage
14. isUserMessage
15. Constants
16. adminMessage
17. adminMessageUpdate
18. broadcastMessage
19. deleteMessage
20. delivery
21. enter
22. error
23. exit
24. fileMessage
25. fileMessageUpdate
26. login
27. mack
28. memberCountChange
29. ping
30. pollUpdate
31. pollVote
32. reaction
33. read
34. sessionExpired
35. systemEvent
36. thread
37. typingEnd
38. typingStart
39. userEvent
40. userMessage
41. userMessageUpdate