class_docstr: Test class for observation and state intercepts (which usually do not
  get tested in other models).
code: def update(self, params, **kwargs):
      params = super().update(params, **kwargs)
  
      self["obs_intercept"] = params[:3]
      self["state_intercept"] = params[3:]
  
imports: import numpy
  import pandas
  import os
  import pytest
  from statsmodels.tsa.statespace import mlemodel, sarimax
  from statsmodels import datasets
  from numpy.testing import assert_equal, assert_allclose, assert_raises
label_desc: Use image node_id 4 for calling the Intercepts obj's underlying member method code with example usage: obj.update(params) without return types