code: def _split_indices(self, vec):
      null = pd.isnull(vec)
      ix_obs = np.flatnonzero(~null)
      ix_miss = np.flatnonzero(null)
      if len(ix_obs) == 0:
          raise ValueError(
              "variable to be imputed has no observed values"
          )
      return ix_obs, ix_miss
  
imports: import pandas
  import numpy
  import patsy
  from statsmodels.base.model import LikelihoodModelResults
  from statsmodels.regression.linear_model import OLS
  from collections import defaultdict
label_desc: Use image node_id 4 for calling the MICEData obj's underlying member method code with example usage: obj._split_indices(vec) and returns: ix_obs,  ix_miss