code: def _validate_fixed_params(fixed_params, spec_param_names):
      """
      Check that keys in fixed_params are a subset of spec.param_names except
      "sigma2"
  
      Parameters
      ----------
      fixed_params : dict
      spec_param_names : list of string
          SARIMAXSpecification.param_names
      """
      if fixed_params is None:
          fixed_params = {}
  
      assert isinstance(fixed_params, dict)
  
      fixed_param_names = set(fixed_params.keys())
      valid_param_names = set(spec_param_names) - {"sigma2"}
  
      invalid_param_names = fixed_param_names - valid_param_names
  
      if len(invalid_param_names) > 0:
          raise ValueError(
              f"Invalid fixed parameter(s): {sorted(list(invalid_param_names))}."
              f" Please select among {sorted(list(valid_param_names))}."
          )
  
      return fixed_params
  
file_path: statsmodels/statsmodels/tsa/arima/estimators/hannan_rissanen.py
imports: import numpy
  from scipy.signal import lfilter
  from statsmodels.tools.tools import Bunch
  from statsmodels.regression.linear_model import OLS, yule_walker
  from statsmodels.tsa.tsatools import lagmat
  from statsmodels.tsa.arima.specification import SARIMAXSpecification
  from statsmodels.tsa.arima.params import SARIMAXParams
label_desc: Use image node_id 2 for calling a global function with example usage: _validate_fixed_params(fixed_params, spec_param_names) and returns: fixed_params