code: def mse(y_true, y_pred):
      return (y_true - y_pred) ** 2
  
imports: import numpy
  from keras import testing
  from keras.metrics import reduction_metrics
  from keras.saving import register_keras_serializable
label_desc: Use image node_id 1 for calling a global function with example usage: mse(y_true, y_pred) and returns: unknown