For example: application/cphl+json will return the _definition and _links collections, but omit the "code" property for the different _links actions as well as the content-types available under "formats."
application/cphl+json+code will return the _definition and _links collections, but omit the formats property.
application/cphl+json+code+formats will include both the code and formats properties.
application/cphl+json+formats will include the formats property, but continue to exclude the code properties.