Instantiate a new instance of the class into which we are included and populate that instance‘s attributes given the provided Hash. Key names in the Hash should map to attribute names on the model.

Declares an attribute named ::symbol:: which can be set with either an instance of ::klass:: or a Hash which will be used to populate a new instance of ::klass::.

Declares an attribute named ::symbol:: which can be set with either a list of instances of ::klass:: or a list of Hashes which will be used to populate a new instance of ::klass::.

Create a standard attr_writer and a populating_attr_reader

Create a reader that will attempt to populate the model if it has not already been populated