private void empower() {
        expression.setDelegate(new ExpressionDelegate(metricName, literal));
        extendNumber(Number.class);
    }
Run the expression with a data map.

@param sampleFamilies a data map includes all of candidates to be analysis.
@return The result of execution.
oap-server/analyzer/meter-analyzer/src/main/java/org/apache/skywalking/oap/meter/analyzer/dsl/Expression.java