code: public boolean isSorted(String sortExpression) {
          if(sortExpression == null)
              return false;
  
          Sort term = findSort(sortExpression);
          if(term == null || term.getDirection() == SortDirection.NONE)
              return false;
          else return true;
      }
docs: Check to see if the SortModel contains a {@link Sort} whose sort expression matches the given
  <code>sortExpression</code>.
  
  @param sortExpression the sortExpression used to locate a {@link Sort}
  @return <code>true</code> if a {@link Sort} is found whose {@link Sort#getSortExpression()} matches
  the given <code>sortExpression</code>.  <code>false</code> otherwise.