default int indexOf(final Object element) {
		return indexOf(element, 0, length());
	}
Returns the index of the first 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}
@return the index of the first occurrence of the specified element in
         this sequence, or -1 if this sequence does not contain the element
jenetics/src/main/java/io/jenetics/util/Seq.java