class_docstr: This class is used for saving the validation loss and the training loss per epoch.
docstr: Save the loss of training and validation set at the end of each epoch.
code: def on_epoch_end(self, epoch, logs={}):
      """Save the loss of training and validation set at the end of each epoch."""
      self.losses.append(logs.get("loss"))
      self.val_losses.append(logs.get("val_loss"))
  
imports: import numpy
  import matplotlib.pyplot
  import seaborn
  from recommenders.evaluation.python_evaluation import ndcg_at_k
  import tensorflow
  from tensorflow.keras.layers import *
  from tensorflow.keras.models import Model
  from tensorflow.keras import backend
  from tensorflow.keras.callbacks import ReduceLROnPlateau, Callback
label_desc: Use image node_id 2 for calling the LossHistory obj's underlying member method code with example usage: obj.on_epoch_end(epoch, logs) without return types