code: def relative_error(y_hat, y_exact):
      return nd.max(
          nd.max(nd.abs(y_exact - y_hat), axis=1)
          / nd.max(nd.abs(y_exact), axis=1)
      )
  
imports: import numpy
  import pytest
  from mxnet import nd
  from gluonts.mx.model.gp_forecaster.gaussian_process import GaussianProcess
  from gluonts.mx.kernels import RBFKernel
  from .data import load_exact_mean, load_exact_std, load_gp_params, load_xfull, load_ytrain
label_desc: Use image node_id 1 for calling a global function with example usage: relative_error(y_hat, y_exact) and returns: nd