How to use $builder->context and $builder->fromContext

There doesn't seems to be any documentation for this but the comments it seems to suggest you can set a context in one resolver and retrieve that value later on in another resolver, i was hoping something like the following but it doesn't work

```
$registry->addFieldResolver(
'ImageGridParagraph', 'style',
$builder->compose(
$builder->produce('property_path')
->map('type', $builder->fromValue('entity:paragraph'))
->map('value', $builder->fromParent())
->map('path', $builder->fromValue('field_image_focal_point_styles.value')),
$builder->context(
'image-grid-style', $builder->fromParent()
),
)
);
```

```
$registry->addFieldResolver(
'Image', 'parentStyle',
$builder->compose(
$builder->fromContext('image-grid-style'),
)
);
```
I want to pass a value a couple of levels down a nested structure