Summary:
`renderItem` on `SectionList` is within the `OptionalProps` group of props but it is not actually marked as optional. Which means that doing things such as in the example where each section has its own `renderItem` and no `renderItem` prop is passed into `SectionList` will fail flow.
Create a `SectionList` where each section has it's own `renderItem` and do not pass in a `renderItem` into `SectionList`. Run flow, it should error.
[GENERAL] [MINOR] [SectionList] -Makes `renderItem` prop on `SectionList` optional for flow.
Closes https://github.com/facebook/react-native/pull/17262
Differential Revision: D6645672
Pulled By: hramos
fbshipit-source-id: 1096e8c4998c14003cf42f29ea559505082047c1
a8391bde7d