public String toString(String format) {
        return String.format(format, getLeft(), getRight());
    }
<p>Formats the receiver using the given format.</p>

<p>This uses {@link java.util.Formattable} to perform the formatting. Two variables may
be used to embed the left and right elements. Use {@code %1$s} for the left
element (key) and {@code %2$s} for the right element (value).
The default format used by {@code toString()} is {@code (%1$s,%2$s)}.</p>

@param format  the format string, optionally containing {@code %1$s} and {@code %2$s}, not null
@return the formatted string, not null
android/android_framework/base/src/main/java/lang3/tuple/Pair.java