code: @Pure
  	public static ClearableReference<Skill> getInternalSkillReference(Agent agent, Class<? extends Capacity> type) {
  		return agent.$getSkill(type);
  	}
docs: Replies the internal skill reference of an agent.
  
  @param agent the agent.
  @param type the type of the capacity.
  @return the skill reference
  @throws UnimplementedCapacityException if the agent has not a skill for the given capacity.
  @since 0.6