def add_capability!(capability)
	        raise PbwArgumentError('Invalid capability') unless capability
	        return false if has_capability?(capability)
	        return false unless capability.before_add(self)
	        self.capabilities << capability
	        save!
	        capability.after_add(self)
	        self
	    end
def add_capability!(capability)
	        raise PbwArgumentError('Invalid capability') unless capability
	        return false if has_capability?(capability)
	        return false unless capability.before_add(self)
	        self.capabilities << capability
	        save!
	        capability.after_add(self)
	        self
	    end
CAPABILITIES