code: public List<ExpressionMapping> getInputOnlyExpressionMappings() {
          List<ExpressionMapping> list = new LinkedList<ExpressionMapping>();
          for (ExpressionMapping em : _inputExpressionMappings) {
              if (em.getOutput() == null) {
                  list.add(em);
              }
          }
          return list;
      }
docs: Gets the input-only expression mappings.
  
  @return the input-only expression mappings