@Override
    public String getProperty(String key) {
        return resolveEnvVars(super.getProperty(key));
    }
@Test
    public void getProperty() throws Exception {
        SystemLambda.withEnvironmentVariable("NC_PORT", "6667").execute(() -> {
            System.setProperty("propertiesImplementation",
                    "org.apache.pulsar.io.flume.node.EnvVarResolverProperties");

            assertEquals(provider.getFlumeConfiguration()
                    .getConfigurationFor("a1")
                    .getSourceContext().get("r1").getParameters().get("port"), "6667");
        });
    }