code: public DiffReport performDiff(FastBlobStateEngine fromState, FastBlobStateEngine toState) throws DiffReportGenerationException {
          return performDiff(null, fromState, toState);
      }
docs: Perform a diff between two data states.
  
  Note:  For now, this operation will ignore type instructions for non-unique keys.
  
  @param fromState - The "from" state engine, populated with one of the deserialized data states to compare
  @param toState - the "to" state engine, populated with the other deserialized data state to compare.
  @param factory - The SerializerFactory describing the data model to use.
  @return the DiffReport for investigation of the differences between the two data states.
  @throws DiffReportGenerationException