code: private static void validateReservedVariableNames( Graph graph, List<String> errors ){
          for( Node node : graph.getNodes() ){
              if( node instanceof BeanAsyncCallActivity ){
                  validateReservedVariablesFromMapping( ((BeanAsyncCallActivity)node).getResultMapping(), graph, node, errors );
              }
              else if( node instanceof BeanCallActivity ){
                  validateReservedVariablesFromMapping( ((BeanCallActivity)node).getResultMapping(), graph, node, errors );
              }
              else if( node instanceof CreateNewInstanceActivity ){
                  MapMapping mapMapping = ((CreateNewInstanceActivity)node).getArgumentsMapping();
                  if( mapMapping != null && mapMapping.getEntryMappings() != null ){
                      for( String key : mapMapping.getEntryMappings().keySet() ){
                          validateReservedVariable( key, graph, node, errors );
                      }
                  }
              }
              else if( node instanceof HumanTaskActivity ){
                  validateReservedVariablesFromMapping( ((HumanTaskActivity)node).getResultMapping(), graph, node, errors );
              }
              else if( node instanceof ObjectCallActivity ){
                  validateReservedVariablesFromMapping( ((ObjectCallActivity)node).getResultMapping(), graph, node, errors );
              }
              else if( node instanceof SetAttributeActivity ){
                  validateReservedVariable( ((SetAttributeActivity)node).getAttribute(), graph, node, errors );
              }
              else if( node instanceof CatchSignal ){
                  validateReservedVariablesFromMapping( ((CatchSignal)node).getResultMapping(), graph, node, errors );
              }
          }
      }
docs: check through all the node types which use mappings which set Environment attributes