code: def msemetric_np(y_pred, y):
      return np.mean((flatten(y_pred) - flatten(y)) ** 2)
  
imports: from __future__ import annotations
  import unittest
  import numpy
  import torch
  import torch.distributed
  from ignite.engine import Engine
  from monai.handlers import MeanAbsoluteError, MeanSquaredError, PeakSignalToNoiseRatio, RootMeanSquaredError
  from monai.utils import set_determinism
  from tests.utils import DistCall, DistTestCase
label_desc: Use image node_id 2 for calling a global function with example usage: msemetric_np(y_pred, y) and returns: np