NestingGroup is similar to NestingSingle in that it calls for only a single instance of a given block type with no labels, but it additonally guarantees that its result will never be null, even if the block is absent, and instead the nested attributes and blocks will be treated as absent in that case.

NestingList indicates that multiple blocks of the given type are permitted, with no labels, and that their corresponding objects should be provided in a list.

NestingMap indicates that multiple blocks of the given type are permitted, each with a single label, and that their corresponding objects should be provided in a map whose keys are the labels.

NestingSet indicates that multiple blocks of the given type are permitted, with no labels, and that their corresponding objects should be provided in a set.

NestingSingle indicates that only a single instance of a given block type is permitted, with no labels, and its content should be provided directly as an object value.

Attribute represents a configuration attribute, within a block.

Block represents a configuration block.

NestedBlock represents the embedding of one block within another.

Object represents the embedding of a structural object inside an Attribute.

NestingMode is an enumeration of modes for nesting blocks inside other blocks.