anchor.diff:  
   *Parcel will error if the generic parameter is not mapped.
   
  +==== Polymorphism
  +Note that Parceler does not unwrap inheritance hierarchies, so any polymorphic
  +fields will be unwrapped as instances of the base class. This is because Parceler
  +opts for performance rather than checking `.getClass()` for every piece of data.
  +[source,java]
  +----
  +@Parcel
  +public class Example {
  +    public Parent p;
  +    Example(Parent p) { this.p = p; }
  +}
  +
  +@Parcel public class Parent {}
  +@Parcel public class Child extends Parent {}
  +----
  +
  +[source,java]
  +----
  +Example example = new Example(new Child());
  +System.out.println("%b", example.p instanceof Child); // true
  +example = Parcels.unwrap(Parcels.wrap(example));
  +System.out.println("%b", example.p instanceof Child); // false
  +----
  +
  +Refer to the <<custom-serialization,Custom Serialization>> section for an example of working with
  +polymorphic fields.
  +
  +=== Serialization techniques
  +
  +Parceler offers several choices for how to serialize and deserialize an object
  +in addition to the field-based serialization seen above.
  +
  +==== Getter/setter serialization
   Parceler may be configured to serialize using getter and setter methods and a non-empty constructor.
   In addition, fields, methods and constructor parameters may be associated using the +@ParcelParameter+ annotation.
   This supports a number of bean strategies including immutability and traditional getter/setter beans.
  
positive.code: Example example = Parcels.unwrap(this.getIntent().getExtras().get("example"));
  ----
  
  Only a select number of types may be used as attributes of a +@Parcel+ class.  The following list includes the mapped
  types:
  
  
negative.code: 
  If an empty constructor is present, Parceler will use that constructor unless another constructor is annotated.
  
  ==== Mixing getters/setters and fields
  You may also mix and match serialization techniques using the +@ParcelParameter+ annotation.
  In the following example, +firstName+ and +lastName+ are written to the bean using the constructor while +firstName+
  is read from the bean using the field and +lastName+ is read using the +getLastName()+ method.  The parameters +firstName+
  