default int lastIndexOf(
		final Object element,
		final int start,
		final int end
	) {
		return element != null
			? lastIndexWhere(element::equals, start, end)
			: lastIndexWhere(Objects::isNull, start, end);
	}
Returns the index of the last occurrence of the specified element
in this sequence, or -1 if this sequence does not contain the element.

@param element element to search for, can be {@code null}
@param start the search start index
@param end the search end index
@return the index of the last occurrence of the specified element in
        this sequence, or -1 if this sequence does not contain the element
@throws IndexOutOfBoundsException for an illegal end point index value
         ({@code start < 0 || end > length() || start > end}).
jenetics/src/main/java/io/jenetics/util/Seq.java