clearSerial method Null safety

1. printersdk
2. printer.pb
3. UsbAccessoryDevice
4. clearSerial method

UsbAccessoryDevice class

1. Constructors
2. UsbAccessoryDevice
3. fromBuffer
4. fromJson
5. Properties
6. description
7. eventPlugin
8. hashCode
9. info_
10. isFrozen
11. manufacturer
12. model
13. runtimeType
14. serial
15. type
16. unknownFields
17. uri
18. version
19. Methods
20. $_ensure
21. $_get
22. $_getB
23. $_getBF
24. $_getI
25. $_getI64
26. $_getIZ
27. $_getList
28. $_getMap
29. $_getN
30. $_getS
31. $_getSZ
32. $_has
33. $_setBool
34. $_setBytes
35. $_setDouble
36. $_setFloat
37. $_setInt64
38. $_setSignedInt32
39. $_setString
40. $_setUnsignedInt32
41. $_whichOneof
42. addExtension
43. check
44. clear
45. clearDescription
46. clearExtension
47. clearField
48. clearManufacturer
49. clearModel
50. clearSerial
51. clearType
52. clearUri
53. clearVersion
54. clone
55. copyWith
56. createEmptyInstance
57. createMapField
58. createRepeatedField
59. ensureType
60. extensionsAreInitialized
61. freeze
62. getDefaultForField
63. getExtension
64. getField
65. getFieldOrNull
66. getTagNumber
67. hasDescription
68. hasExtension
69. hasField
70. hasManufacturer
71. hasModel
72. hasRequiredFields
73. hasSerial
74. hasType
75. hasUri
76. hasVersion
77. isInitialized
78. mergeFromBuffer
79. mergeFromCodedBufferReader
80. mergeFromJson
81. mergeFromJsonMap
82. mergeFromMessage
83. mergeFromProto3Json
84. mergeUnknownFields
85. noSuchMethod
86. setExtension
87. setField
88. toBuilder
89. toDebugString
90. toProto3Json
91. toString
92. writeToBuffer
93. writeToCodedBufferWriter
94. writeToJson
95. writeToJsonMap
96. Operators
97. operator ==
98. Static methods
99. create
100. createRepeated
101. getDefault