code: def values(self, index):
          
          values = []
          for i in xrange(self.num_instances):
              inst = self.get_instance(i)
              values.append(inst.get_value(index))
          return numpy.array(values)
docs: Returns the internal values of this attribute from all the instance objects.
  
          :return: the values as numpy array
          :rtype: list