clearOutputUriPrefix method Null safety

1. spine_client
2. operation.pb
3. ExportDocumentsMetadata
4. clearOutputUriPrefix method

ExportDocumentsMetadata class

1. Constructors
2. ExportDocumentsMetadata
3. fromBuffer
4. fromJson
5. Properties
6. collectionIds
7. endTime
8. eventPlugin
9. hashCode
10. info_
11. isFrozen
12. operationState
13. outputUriPrefix
14. progressBytes
15. progressDocuments
16. runtimeType
17. startTime
18. unknownFields
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. clearEndTime
46. clearExtension
47. clearField
48. clearOperationState
49. clearOutputUriPrefix
50. clearProgressBytes
51. clearProgressDocuments
52. clearStartTime
53. clone
54. copyWith
55. createEmptyInstance
56. createMapField
57. createRepeatedField
58. ensureEndTime
59. ensureProgressBytes
60. ensureProgressDocuments
61. ensureStartTime
62. extensionsAreInitialized
63. freeze
64. getDefaultForField
65. getExtension
66. getField
67. getFieldOrNull
68. getTagNumber
69. hasEndTime
70. hasExtension
71. hasField
72. hasOperationState
73. hasOutputUriPrefix
74. hasProgressBytes
75. hasProgressDocuments
76. hasRequiredFields
77. hasStartTime
78. isInitialized
79. mergeFromBuffer
80. mergeFromCodedBufferReader
81. mergeFromJson
82. mergeFromJsonMap
83. mergeFromMessage
84. mergeFromProto3Json
85. mergeUnknownFields
86. noSuchMethod
87. setExtension
88. setField
89. toBuilder
90. toDebugString
91. toProto3Json
92. toString
93. writeToBuffer
94. writeToCodedBufferWriter
95. writeToJson
96. writeToJsonMap
97. Operators
98. operator ==
99. Static methods
100. create
101. createRepeated
102. getDefault