@Override
    public VariableResolver setIndexedVariableResolver(int index, VariableResolver variableResolver) {
        return null;
    }
@see org.mvel2.integration.impl.BaseVariableResolverFactory#setIndexedVariableResolver(int, org.mvel2.integration.VariableResolver)
test/common/src/main/java/io/apiman/test/common/util/TestVariableResolverFactory.java