private void handleInitExp(String exp) {
        Expression e = DSL.parse(null, exp);
        final Result result = e.run(ImmutableMap.of());
        if (!result.isSuccess() && result.isThrowable()) {
            throw new ExpressionParsingException(
                "failed to execute init expression: " + exp + ", error:" + result.getError());
        }
    }
toMeter transforms {@link SampleFamily} collection  to meter-system metrics.

@param sampleFamilies {@link SampleFamily} collection.
oap-server/analyzer/meter-analyzer/src/main/java/org/apache/skywalking/oap/meter/analyzer/MetricConvert.java