docs: public static Matcher<VariableTree> variableInitializer(
        final Matcher<ExpressionTree> expressionTreeMatcher) {
      return new Matcher<VariableTree>() {
        @Override
        public boolean matches(VariableTree variableTree, VisitorState state) {
          ExpressionTree initializer = variableTree.getInitializer();
          return initializer == null ? false : expressionTreeMatcher.matches(initializer, state);
        }
      };
    }