@Test
    public void shouldSupplyMeanNumberInstance() {
        assertThat(MeanNumberSupplier.instance().get(), instanceOf(MeanGlobalStep.MeanNumber.class));
    }
@author Stephen Mallette (http://stephen.genoprime.com)
gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/util/function/MeanNumberSupplierTest.java