code: def ks_stat_and_mse(df, h0_intercept):
      """Run Kolmogorov-Smirnov test and compute Mean Squared Error"""
      kstest_pval = stats.kstest(h0_intercept, stats.t(df).cdf)[1]
      mse = mean_squared_error(df=df, h0_intercept=h0_intercept)
      return kstest_pval, mse
  
imports: import nibabel
  import numpy
  import pytest
  from numpy.testing import assert_array_almost_equal, assert_array_less, assert_equal
  from scipy import stats
  from nilearn.conftest import _rng
  from nilearn.maskers import NiftiMasker
  from nilearn.mass_univariate import permuted_ols
label_desc: Use image node_id 13 for calling a global function with example usage: ks_stat_and_mse(df, h0_intercept) and returns: kstest_pval,  mse