code: private static void checkParams(final Builder paramBuilder) {
          checkState(paramBuilder.mSession != null && paramBuilder.mKey >= 0 && paramBuilder.mNewRev >= 0
              && paramBuilder.mOldRev >= 0 && paramBuilder.mObservers != null && paramBuilder.mKind != null,
              "No valid arguments specified!");
          checkState(
              paramBuilder.mNewRev != paramBuilder.mOldRev && paramBuilder.mNewRev >= paramBuilder.mOldRev,
              "Revision numbers must not be the same and the new revision must have a greater number than the old revision!");
      }
docs: Check parameters for validity and assign global static variables.
  
  @param paramBuilder
  {@link Builder} reference