hollow/src/main/java/com/netflix/hollow/core/write/objectmapper/HollowObjectMapper.java
public int add(Object o) {
        HollowTypeMapper typeMapper = getTypeMapper(o.getClass(), null, null);
        return typeMapper.write(o);
    }
public int add(Object o) {
        HollowTypeMapper typeMapper = getTypeMapper(o.getClass(), null, null);
        return typeMapper.write(o);
    }
Adds the specified POJO to the state engine.
<p>
Unless previously initialized with {@link #initializeTypeState(Class)},
the first time an instance of a particular type is added
its schema is derived and added to the data model.

@param o the POJO to add
@return the ordinal assigned to the newly added object