@NonNull
    public String keyFor(@NonNull String id) {
        return id;
    }
@Test
    public void testKeyForCaseSensitiveEmailAddress() {
        IdStrategy idStrategy = new IdStrategy.CaseSensitiveEmailAddress();
        assertThat(idStrategy.keyFor("john.smith@acme.org"), is("john.smith@acme.org"));
        assertThat(idStrategy.keyFor("John.Smith@acme.org"), is("John.Smith@acme.org"));
        assertThat(idStrategy.keyFor("John.Smith@ACME.org"), is("John.Smith@acme.org"));
        assertThat(idStrategy.keyFor("John.Smith@acme.ORG"), is("John.Smith@acme.org"));
        assertThat(idStrategy.keyFor("john.smith"), is("john.smith"));
        assertThat(idStrategy.keyFor("John.Smith"), is("John.Smith"));
        assertThat(idStrategy.keyFor("john@smith@acme.org"), is("john@smith@acme.org"));
        assertThat(idStrategy.keyFor("John@Smith@acme.org"), is("John@Smith@acme.org"));
    }