old_contents: from .ar_model import AR
  from .arima_model import ARMA, ARIMA
  from . import vector_ar as var
  from .arima_process import arma_generate_sample, ArmaProcess
  from .vector_ar.var_model import VAR
  from .vector_ar.svar_model import SVAR
  from .vector_ar.dynamic import DynamicVAR
  from .filters import api as filters
  from . import tsatools
  from .tsatools import (add_trend, detrend, lagmat, lagmat2ds, add_lag)
  from . import interp
  from . import stattools
  from .stattools import *
  from .base import datetools
  from .seasonal import seasonal_decompose
  from ..graphics import tsaplots as graphics
  from .x13 import x13_arima_select_order
  from .x13 import x13_arima_analysis
  from .statespace import api as statespace
  from .statespace.sarimax import SARIMAX
  from .statespace.structural import UnobservedComponents
  from .statespace.varmax import VARMAX
  from .statespace.dynamic_factor import DynamicFactor
  
new_contents: from .ar_model import AR
  from .arima_model import ARMA, ARIMA
  from . import vector_ar as var
  from .arima_process import arma_generate_sample, ArmaProcess
  from .vector_ar.var_model import VAR
  from .vector_ar.svar_model import SVAR
  from .vector_ar.dynamic import DynamicVAR
  from .filters import api as filters
  from . import tsatools
  from .tsatools import (add_trend, detrend, lagmat, lagmat2ds, add_lag)
  from . import interp
  from . import stattools
  from .stattools import *
  from .base import datetools
  from .seasonal import seasonal_decompose
  from ..graphics import tsaplots as graphics
  from .x13 import x13_arima_select_order
  from .x13 import x13_arima_analysis
  from .statespace import api as statespace
  from .statespace.sarimax import SARIMAX
  from .statespace.structural import UnobservedComponents
  from .statespace.varmax import VARMAX
  from .statespace.dynamic_factor import DynamicFactor
  from .regime_switching.markov_regression import MarkovRegression
  from .regime_switching.markov_autoregression import MarkovAutoregression
subject: Add switching models to tsa api