lenses.kt

// lens focusing on the path variable name
val nameLens = Path.string().of("name")

// lens focusing on a required query parameter city
val requiredQuery = Query.required("city")

// lens focusing on a required and non-empty string city 
val nonEmptyQuery = Query.nonEmptyString().required("city")

// lens focusing on an optional header Content-Length with type int 
val optionalHeader = Header.int().optional("Content-Length")

// lens focusing on text body
val responseBody = Body.string(ContentType.TEXT_PLAIN).toLens()