code: def mse_loss(x, error):
      return np.dot(np.dot(x, error), x.T)
  
file_path: ReAgent/reagent/evaluation/weighted_sequential_doubly_robust_estimator.py
imports: import itertools
  import logging
  import numpy
  import scipy
  from reagent.evaluation.cpe import CpeEstimate
  from reagent.evaluation.evaluation_data_page import EvaluationDataPage
label_desc: Use image node_id 1 for calling a global function with example usage: mse_loss(x, error) and returns: np