code: private Node newBranchInstrumentationNode(NodeTraversal traversal, Node node, int idx) {
      String arrayName = createArrayName(traversal);
  
      // Create instrumentation Node
      Node getElemNode = IR.getelem(IR.name(arrayName), IR.number(idx)); // Make line number 0-based
      Node exprNode = IR.exprResult(IR.assign(getElemNode, IR.trueNode()));
  
      // Note line as instrumented
      String fileName = traversal.getSourceName();
      if (!instrumentationData.containsKey(fileName)) {
        instrumentationData.put(fileName, new FileInstrumentationData(fileName, arrayName));
      }
      return exprNode.useSourceInfoIfMissingFromForTree(node);
    }
docs: Create an assignment to the branch coverage data for the given index into the array.
  
  @return the newly constructed assignment node.