code: public SyntheticProperty addKeyProperty(String name, Direction direction) {
          StorableProperty<S> prop = mMasterStorableInfo.getAllProperties().get(name);
          if (prop == null) {
              throw new IllegalArgumentException(name + " is not a property of "
                      + mMasterStorableInfo.getName());
          }
  
          mPrimaryKey.addProperty(name, direction);
  
          SyntheticProperty result = addProperty(prop);
          mUserProps.add(result);
          return result;
      }
docs: Add a property to the primary key which is a member of the Storable type
  being referenced by this one.
  
  @param name