Group of nilpotency class two whose derived subgroup is 2-divisible

Definition
A group $$G$$ is termed a group of nilpotency class two whose derived subgroup is 2-divisible if it satisfies both the following conditions:


 * 1) $$G$$ is a group of nilpotency class two.
 * 2) The derived subgroup $$G'$$ is a 2-divisible group, i.e., every element of the derived subgroup has a square root in the derived subgroup.