code: public JsonMappingOption asFieldNaming(JsonFieldNaming fieldNaming) {
          if (fieldNaming == null) {
              throw new IllegalArgumentException("The argument 'fieldNaming' should not be null.");
          }
          this.fieldNaming = OptionalThing.of(fieldNaming);
          return this;
      }
docs: Set up as list-null-to-empty writing. (null value of List is writtern as empty list)
  @param fieldNaming The type of field naming. (NotNull)
  @return this. (NotNull)