maximum property Null safety

1. conduit_open_api
2. open_api_v2
3. APISchemaObject
4. maximum property

APISchemaObject class

1. Constructors
2. APISchemaObject
3. Properties
4. additionalProperties
5. castMap
6. collectionFormat
7. defaultValue
8. description
9. enumerated
10. example
11. exclusiveMaximum
12. exclusiveMinimum
13. extensions
14. format
15. hashCode
16. isRequired
17. items
18. maximum
19. maxItems
20. maxLength
21. minimum
22. minItems
23. minLength
24. multipleOf
25. pattern
26. properties
27. readOnly
28. referenceURI
29. representation
30. runtimeType
31. title
32. type
33. uniqueItems
34. Methods
35. decode
36. encode
37. noSuchMethod
38. toString
39. Operators
40. operator ==