code: public boolean isNullable() {
          if (mPrime.isNullable()) {
              return true;
          }
          if (mChain != null) {
              for (StorableProperty<?> prop : mChain) {
                  if (prop.isNullable()) {
                      return true;
                  }
              }
          }
          return false;
      }
docs: Returns true if any property in the chain can be null.
  
  @see com.amazon.carbonado.Nullable
  @since 1.2