code: def bprop(self, error, alpha=1.0, beta=0.0):
      raise NotImplementedError
  
imports: from neon.layers.layer import Layer, ParameterLayer
  import numpy
  from neon.transforms import Softmax
  from neon.initializers.initializer import Constant
  import math
  from collections import OrderedDict
label_desc: Use image node_id 5 for calling the PriorBox obj's underlying member method code with example usage: obj.bprop(error, alpha, beta) without return types