public Genotype<G> genotype() {
		return _genotype;
	}
This method returns a copy of the {@code Genotype}, to guarantee a
immutable class.

@return the cloned {@code Genotype} of this {@code Phenotype}.
@throws NullPointerException if one of the arguments is {@code null}.
jenetics/src/main/java/io/jenetics/Phenotype.java