code: def _check_margeff_args(at, method):
      """
      Checks valid options for margeff
      """
      if at not in ["overall", "mean", "median", "zero", "all"]:
          raise ValueError("%s not a valid option for `at`." % at)
      if method not in ["dydx", "eyex", "dyex", "eydx"]:
          raise ValueError("method is not understood.  Got %s" % method)
  
imports: from statsmodels.compat.python import lzip
  import numpy
  from scipy.stats import norm
  from statsmodels.tools.decorators import cache_readonly
label_desc: Use image node_id 1 for calling a global function with example usage: _check_margeff_args(at, method) without return types