@Override
    public String toString() {
        return value != null
                ? String.format("Optional[%s]", value)
                : "Optional.empty";
    }
Returns a non-empty string representation of this Optional suitable for
debugging. The exact presentation format is unspecified and may vary
between implementations and versions.

@return the string representation of this instance
@implSpec If a value is present the result must include its string
representation in the result. Empty and present Optionals must be
unambiguously differentiable.
android/android_framework/base/src/main/java/github/tornaco/android/thanos/core/util/Optional.java