searchFields property Null safety

1. sendbird_sdk
2. group_channel_list_query
3. GroupChannelListQuery
4. searchFields property

GroupChannelListQuery class

1. Constructors
2. GroupChannelListQuery
3. Properties
4. channelHiddenStateFilter
5. channelNameContains
6. channelUrls
7. customTypes
8. customTypeStartWith
9. hashCode
10. hasNext
11. includeEmptyChannel
12. includeFrozenChannel
13. includeMemberList
14. includeMetaData
15. limit
16. loading
17. memberStateFilter
18. metaDataKeyFilter
19. metaDataOrderKeyFilter
20. metaDataValuesFilter
21. metaDataValueStartWithFilter
22. nicknameContains
23. order
24. publicChannelFilter
25. queryType
26. runtimeType
27. searchFields
28. searchQuery
29. superChannelFilter
30. token
31. unreadChannelFilter
32. userIdsExactlyIn
33. userIdsIncludeIn
34. Methods
35. loadNext
36. noSuchMethod
37. setChannelUrlsFilter
38. setMetaDataFilterWithStartWith
39. setMetaDataFilterWithValues
40. setNicknameContainsFilter
41. setSearchFilter
42. setUserIdsExactFilter
43. setUserIdsIncludeFilter
44. toJson
45. toString
46. Operators
47. operator ==