code: @Nullable
    public static ExpressionTree getArgument(AnnotationTree annotationTree, String name) {
      for (ExpressionTree argumentTree : annotationTree.getArguments()) {
        if (argumentTree.getKind() != Tree.Kind.ASSIGNMENT) {
          continue;
        }
        AssignmentTree assignmentTree = (AssignmentTree) argumentTree;
        if (!assignmentTree.getVariable().toString().equals(name)) {
          continue;
        }
        ExpressionTree expressionTree = assignmentTree.getExpression();
        return expressionTree;
      }
      return null;
    }
docs: Gets the value for an argument, or null if the argument does not exist.
  
  @param annotationTree the AST node for the annotation
  @param name the name of the argument whose value to get
  @return the value of the argument, or null if the argument does not exist