docs: public static List<ExpressionTree> parseExpressions(
                                              final List<String> expressions, 
                                              final TSQuery ts_query, 
                                              final List<String> metric_queries) {
      final List<ExpressionTree> trees = 
          new ArrayList<ExpressionTree>(expressions.size());
      for (final String expr: expressions) {
        final SyntaxChecker checker = new SyntaxChecker(new StringReader(expr));
        checker.setMetricQueries(metric_queries);
        checker.setTSQuery(ts_query);
        try {
          trees.add(checker.EXPRESSION());
        } catch (ParseException e) {
          throw new IllegalArgumentException("Failed to parse " + expr, e);
        }
      }
      return trees;
    }