class_docstr: SARIMAX parameters.
  
  Parameters
  ----------
  spec : SARIMAXSpecification
      Specification of the SARIMAX model.
  
  Attributes
  ----------
  spec : SARIMAXSpecification
      Specification of the SARIMAX model.
  exog_names : list of str
      Names associated with exogenous parameters.
  ar_names : list of str
      Names associated with (non-seasonal) autoregressive parameters.
  ma_names : list of str
      Names associated with (non-seasonal) moving average parameters.
  seasonal_ar_names : list of str
      Names associated with seasonal autoregressive parameters.
  seasonal_ma_names : list of str
      Names associated with seasonal moving average parameters.
  param_names :list of str
      Names of all model parameters.
  k_exog_params : int
      Number of parameters associated with exogenous variables.
  k_ar_params : int
      Number of parameters associated with (non-seasonal) autoregressive
      lags.
  k_ma_params : int
      Number of parameters associated with (non-seasonal) moving average
      lags.
  k_seasonal_ar_params : int
      Number of parameters associated with seasonal autoregressive lags.
  k_seasonal_ma_params : int
      Number of parameters associated with seasonal moving average lags.
  k_params : int
      Total number of model parameters.
code: def ar_poly(self, value):
      # Convert from the polynomial to the parameters, and set that way
      if isinstance(value, Polynomial):
          value = value.coef
      value = validate_basic(
          value, self.spec.max_ar_order + 1, title="AR polynomial"
      )
      if value[0] != 1:
          raise ValueError("AR polynomial constant must be equal to 1.")
      ar_params = []
      for i in range(1, self.spec.max_ar_order + 1):
          if i in self.spec.ar_lags:
              ar_params.append(-value[i])
          elif value[i] != 0:
              raise ValueError(
                  "AR polynomial includes non-zero values"
                  " for lags that are excluded in the"
                  " specification."
              )
      self.ar_params = ar_params
  
imports: import numpy
  import pandas
  from numpy.polynomial import Polynomial
  from statsmodels.tsa.statespace.tools import is_invertible
  from statsmodels.tsa.arima.tools import validate_basic
label_desc: Use image node_id 7 for calling the SARIMAXParams obj's underlying member method code with example usage: obj.ar_poly(value) without return types