code: def build_P_R_O_nets_from_file(self, weights_file):
      weights = np.load(weights_file, allow_pickle=True).tolist()
  
      p_net = self.build_pnet()
      r_net = self.build_rnet()
      o_net = self.build_onet()
  
      p_net.set_weights(weights["pnet"])
      r_net.set_weights(weights["rnet"])
      o_net.set_weights(weights["onet"])
  
      return p_net, r_net, o_net
  
imports: from tensorflow.keras.layers import Input, Dense, Conv2D, MaxPooling2D, PReLU, Flatten, Softmax
  from tensorflow.keras.models import Model
  import numpy
label_desc: Use image node_id 4 for calling the NetworkFactory obj's underlying member method code with example usage: obj.build_P_R_O_nets_from_file(weights_file) and returns: p_net,  r_net,  o_net