code: def mse(target: np.ndarray, forecast: np.ndarray) -> float:
      r"""
      .. math::
  
          mse = mean((Y - \hat{Y})^2)
  
      See [HA21]_ for more details.
      """
      return np.mean(np.square(target - forecast))
  
file_path: gluonts/src/gluonts/evaluation/metrics.py
imports: from typing import Optional
  import numpy
  from gluonts.time_feature import get_seasonality
label_desc: Use image node_id 2 for calling a global function with example usage: mse(target, forecast) and returns: np