private ContextException addContext(ContextException e) {
    this.context.putAll(e.context);
    return this;
  }
@Test
  public void addContext() {
    ContextException e = ContextException.of(LABEL)
      .addContext("K1", "V1")
      .addContext("K2", "V2");
    assertThat(e).hasMessage(LABEL + " | K1=V1 | K2=V2");
  }