Dependency group operators definition

dep-operators.kt

class DependencyGroup {
  // provides the `.``[]` operators
  operator fun get(key: String): DependencyItem

  // provides the `<key>(<notation>)` syntax
  operator fun String.invoke(notation: String)

  // provides the `<key> {<group>}` syntax
  operator fun String.invoke(init: DependencyGroup.() -> Unit)
}

For article: Defining Dependencies in Gradle Kotlin DS