void checkIndices(final int length) {
			for (int index : indices) {
				if (index >= length) {
					throw new IndexOutOfBoundsException(format(
						"Genotype contains %d Chromosome, but found " +
							"SectionAlterer for Chromosome index %d.",
						length, index
					));
				}
			}
		}
The section class, which defines the chromosomes used by the alterer.
jenetics/src/main/java/io/jenetics/PartialAlterer.java