code: protected static ModelNode convertStringExpression(ModelNode node) {
          if (node.getType() == ModelType.STRING) {
              return ParseUtils.parsePossibleExpression(node.asString());
          }
          return node;
      }
docs: Checks if the given node is of {@link ModelType#STRING} with a string value that includes expression syntax.
  If so returns a node of {@link ModelType#EXPRESSION}, else simply returns {@code node} unchanged
  
  @param node the node to examine. Will not be {@code null}
  @return the node with expressions converted, or the original node if no conversion was performed
  Cannot return {@code null}